福建长乐牛头湾海区浮游植物生态调查

2006年6月13日对福建长乐牛头湾海区进行生态调查,鉴定出浮游植物4门44属94种,平均密度2.51×106个/L,各调查站住均以硅藻为主,其中中肋骨条藻Skeletonema cotatum为绝对优势种,占浮游植物总数量的83%.四个群落结构指数评价结果:牛头湾海区夏季浮游植物生态多样性和均匀度较低,丰度和优势度较高,该海区处于中营养水平.     

基于阀位的主蒸汽流量计算可行性研究

对利用调门综合阀位计算主蒸汽流量需要解决的问题进行了分析,借助某汽轮机正规试验数据,建立了阀位与流量关系的数学模型,并对其相关性、重现性进行了检验。结果表明,当调门重叠度设置合理时,主蒸汽体积流量与综合阀位相关性较强;当调门系统未改变时,调门流量特性重现性较好;主蒸汽流量可由调门综合阀位和主蒸汽参数来求得,作为主蒸汽流量间接测量计算的又一方法,可用于日常离线分析计算。     

大位移井侧位抛物线剖面设计的数值计算

侧位抛物线剖面是大位移井轨道设计中常用的剖面类型。对侧位抛物线剖面设计求解过程中的求侧位抛物线初始点井斜角的数值方法和从段长求井斜角的数值方法进行了分析,指出其关键是求解侧位抛物线初始点井斜角所满足的一个三角函数方程。用倍角公式可将该三角函数方程转化成一个四次代数方程,然后用求根公式直接求出解析解。用解析解可简化侧位抛物线剖面设计过程,减少计算工作量,提高计算速度。侧位抛物线井段参数计算中需要通过段长公式来反求井斜角,给出了反求井斜角的二分法。本文的算法可应用于大位移井轨道设计的软件开发。     

发电集团生态位分析及竞争建议

2002年原国家电力公司拆分为规模相当的五大发电集团及两大电网公司。伴随2002～2005年严重的电力短缺,各新组建的发电集团兴建电厂,力图在新的竞争格局下取得有利地位。在电力建设狂热近5年之后,电力供需矛盾缓解,同时面临着潜在的过剩。本文从企业生态位的视角,分析了发电集团生态位重叠情况,及应采取何种竞争战略,以确保企业在竞争中取得优势地位。     

基于点估计法和随机潮流约束的电网及风电场相关特性研究

针对传统电网多目标规划方法的规划过程中随机变量分布不均,导致精度低、误差大、成本高等问题,以点估计法和随机潮流约束为基础,研究了风电场相关特性,提出相关电网规划方法,通过多项式正态变换技术,对电网内部的不确定因素,即非正态相关变量进行处理,结合最小二乘拟合法计算正态变换项数,引用点估计法确定电网中随机变量的边缘分布和相关性,进行建模,统计分布概率,简化建模模型,通过分析总体样本均值和样本方差均值,确定出量化相关性对电网规划的影响,经过变换得到采样点,进行潮流计算,获得电网输出目标矩阵,实现电网多目标规划,完成风电场相关特性研究。对IEEE-RTS节点进行算例分析,结果表明,基于点估计法和随机潮流约束的电网多目标规划方法具有很强的分析能力,当风电场相关系数达到0.8时,采样值出现极大值和极小值的概率极大增加,规划最大误差小于1.5%,提高了规划效果。     

丁酸型产氢-产酸发酵细菌pH生态位探讨

本试验结果认为,细菌在3 86,或4 5>PH>5 3生态位理论。分析原因在于,试验过程中的环境因素———C/N比的降低,氮源物质浓度的提高,相应提高了微生物的合成代谢水平,并且使得细菌发酵过程在pH值较低的环境中,向合成代谢水平较高的丁酸型发酵转变。细菌发生丁酸型发酵是在环境内多种环境因子协同作用下进行的。该试验结果拓宽了前期理论研究中得到的丁酸型发酵生态位范围,为今后相关的理论研究及实际生产提供了理论依据。     

广西推动工业绿色循环发展

广西坚持发展生态经济,推动工业绿色循环发展,去年规模以上万元工业增加值能耗下降9.3%,产业结构得以持续调整优化。据统计,去年六大高耗能行业总产值占规模以上工业比重为39.8%,下降1.1个百分点;六大高耗能行业投资占工业投资比重为32.6%,下降1.3个百分点。高技术产业增加值增长17.4%,高于规模以上工业6.7个百分点。规模以上工业度电产值22.9元,提高1.9元。自治区工信委相关负责人介绍,去年我区加强工业     

露天矿采煤的生态包袱研究

计算了小型露天矿的生态包袱和生态包袱系数,结果表明,年产90×10^4t的露天煤矿需投入的物质总重量为1543．94×10^4t。生态包袱为1453．94×10^4t,生态包袱系数为17．15t／t煤。计算结果定量反映了露天采煤投入的物质水平以及对生态的压力程度,找出原煤开采的主要生态包袱影响因素,为进一步提出相关对策提供理论依据。     

考虑重叠度的汽轮机调节级变工况改进算法

汽轮机调节级变工况计算对汽轮机的热力校核和在线仿真具有重要意义。通过对调节阀联合升程流量特性的分析,建立相邻两个不完全开启调节阀的流量计算模型,并引入到调节级变工况计算中,提出考虑重叠度的汽轮机调节级变工况改进算法,解决以往重叠区内工况无法计算的问题,保证机组在线仿真的连续性。对国产200MW机组进行调节级变工况计算,结果表明:计算误差在工程设计要求的范围之内,最大为3.07%。     

汽轮机调节汽门重叠度与节流损失之间关系的计算分析

针对目前没有行程重叠度和压力重叠度之间的量化关系这一问题,根据两种重叠度的定义给出了已知行程重叠度时压力重叠度的计算方法,并以某600MW汽轮机为例,计算出其两种重叠度间的数值关系曲线;此外,文中还针对目前无不同重叠度对汽轮机运行经济性影响的量化关系这一问题,对该汽轮机不同重叠度下调节阀节流损失进行计算,结果表明:汽轮机在低于80％最大负荷工况运行时,不同重叠度对汽轮机运行经济性的影响较大,为如何选择汽轮机调门最优重叠度提供了数值依据.     

秦岭山脉典型流域水系分形特征及空间分异性

将分形理论引入流域地貌形态的定量研究,利用盒维数法计算了秦岭地区22个典型流域水系分维值,分析其与流域形态和水文特征的相关性及空间分异性。结果表明,秦岭地区各流域水系在其无标度区间内呈现良好的分形特征,分维值处于1.033 5～1.079 5之间,相关系数达0.979 5以上;各流域水系分维值与流域形状系数呈正相关关系,与年径流深呈负相关关系,与河流比降呈较复杂多项式关系;秦岭山脉南北两侧水系分维值存在一定自组织相关性,尤以秦岭中部及西部地区较为显著,东部地区差异相对较大。     

椭圆钎焊与双金属轧制翅片管传热与阻力性能的试验对比

对椭圆钎焊翅片管和双金属轧制翅片管换热器的传热及阻力性能进行试验对比研究,试验得到了一系列工况下的传热数据与管外空气流动阻力数据,给出了相应的传热系数、流动阻力曲线。从总传热系数中分离出管外空气侧的对流换热系数,得到了具有一定应用价值的管外换热的计算关联式;拟合得到了管外阻力计算关联式。结果表明:椭圆钎焊翅片管比双金属轧制翅片管的传热系数约高9%,管外换热系数约高17%,且管外空气流动阻力约低11%。     

营配调末端融合的供电综合风险预警模型

当前供电营配末端相互独立、关联度偏低,导致其综合风险预警效果较差,为此构建一种新的供电综合风险预警模型。选取供电风险预警指标,并对其进行标准化处理。计算指标间的灰度关联度,并对其进行排序,获取供电风险事件的标量时间序列,求得风险预警的最大梯度差,根据关联指向性特征得到风险预警评估的判决式,以此构建供电风险预警模型。实验结果表明,利用该模型进行供电综合风险预警,预警结果更接近实际结果。     

气门间隙对发动机性能的影响研究

某四缸自然吸气汽油发动机怠速时燃烧不稳定,经热力学性能仿真计算发现怠速时气门重叠角偏大,导致残余废气率较高,从而引起燃烧不稳定及循环变动大。可通过调整进气凸轮轴安装相位或增大气门间隙来推迟进气门开启时刻,减小气门重叠角。本文对加大气门间隙方案做换气过程分析计算,加大气门间隙,气门重叠角减小。在低速时,小的气门重叠角有利于减小废气倒流,提高进气量;但在高速时进气惯性大,由于加大气门间隙,减小了进气迟闭角,造成高速时进气量减小。试验结果验证仿真分析的正确性。试验结果表明,减小气门重叠角可显著改善怠速工况的循环变动和排放,中低速工况的扭矩也有所提升,但高速段功率稍有下降。     

Assessing customer preferences for hydrogen-powered street sweepers: A choice experiment

The large variety of potential hydrogen and fuel cell applications and the associated uncertainties of selecting a particular application pose a challenge for developers in the field: identifying and evaluating promising market niches. Therefore, we conducted an online survey comprising a choice experiment in Switzerland and Germany to assess fleet decision-makers’ preferences for hydrogen-powered street sweepers compared to (more) conventional diesel and compressed natural gas (CNG)/biogas vehicles. The findings indicate that the fleet decision-making structures and vehicle operating practices make street sweeper fleets a promising application for the early implementation of hydrogen fuel cell vehicles. Furthermore, the results show that a market niche for hydrogen-powered sweepers exists in both countries. The choice experiment was a useful approach for the identification of promising market niches and thereby reduces the uncertainties of application selection.     

小生境蚁群-BP神经网络在大坝变形监测中的应用

针对BP神经网络在大坝监测数据预测模型中后期预测精度不高的问题,基于小生境蚁群算法的智能搜索能力和强鲁棒性、BP神经网络对大量的输入-输出模式的非线性映射关系的学习存贮能力,将两种方法结合,用小生境蚁群算法优化BP神经网络的建模方法建立了水平位移观测数据的预测模型,并与ACA-BP神经网络和传统BP神经网络进行了对比分析。结果表明,本文方法可加快BP神经网络收敛速度、增强局部搜索能力,具有更高的预测精度。     

A novel bioenergy feedstock in Latin America? Cultivation potential of Acrocomia aculeata under current and future climate conditions

Plant oil is a key commodity in the global economy, particularly for food and bioenergy markets. However, current production practices often impair smallholder livelihoods, cause land use changes, and compete for food production. The neotropical palm Acrocomia aculeata is currently being promoted as a novel sustainable biomass feedstock, particularly for bioenergy, but only little is known about the palm’s ecological requirements. Based on a comprehensive literature and database search for recorded occurrences of A. aculeata in Latin America, we computed an ecological niche modeling to determine the palm’s potential distribution area based on climatic and soil variables. We subsequently considered current land cover and predicted future climate change scenarios to discuss the cultivation potential of A. aculeata within its possible distribution area. The results revealed a large potential to cultivate A. aculeata in Latin America under current abiotic environmental conditions. The two core distribution regions identified were (1) Central America including the Caribbean, northern Colombia and Venezuela, and (2) southern Brazil and eastern Paraguay. A considerable proportion of the medium to highly suitable growing areas were found to be currently used for agricultural production or covered by land types with high conservation and carbon sequestration value. Applying the model under the IPCC’s A2A ‘business as usual’ emission scenario suggested that by 2080 the vast majority of suitable growing areas severely decline in extent or disappear entirely. Our ecological niche modeling thus shows that despite the palm’s high cultivation potential, a sustainable deployment of A. aculeata requires a precautious, evidence-based approach.     

The country-dependent shaping of ‘hydrogen niche’ formation: A comparative case study of the UK and South Korea from the innovation system perspective

This paper reports an international comparison of hydrogen niche formation in the UK and South Korea with special regard to policy development. Hydrogen energy development has provided us with a good example of ongoing phenomena during the early stage of socio-technical transition, in other words, the socio-technical niche. The purpose of the case studies was to see the country dependence in shaping the early stage (the period between the year 2002 and 2005) of hydrogen niche formation from the national innovation system perspective. The findings show certain differences in the background of hydrogen energy policies and the manners of policy development. There also are differences in the R&D activities, including not only the way in which they are performed, but also the strategic focussing of R&D, which have been influenced by R&D systems and the industrial structures of the national innovation systems. Vision-articulating processes and the roles and tendency towards intervention of governments are diverse. The research result will contribute to better understanding of the geography of socio-technical transition with empirical evidence. From that, one will be hinted that the hydrogen future may be diverse in different locations.     

A Review and Correlations for Convection Heat Transfer and Pressure Losses in Toroidal and Helically Coiled Tubes

The conducted review of the experiments for pressure losses and convection heat transfer in toroidal and coiled tubes yielded 2,410 pressure losses data for water, air, and ethylene glycol flows in 62 different coiled tubes. These data are used to develop a friction factor correlation, in terms of a modified Dean number. The compiled Nusselt number database of 176 data points for flows of water, air, and water–10% and 43.5% glycerol mixtures and additional 17 data points for flows of ethylene glycol, n-amyl alcohol, n-butanol, and n-amyl acetate, with higher Prandtl numbers of 15–175, is correlated in terms of the modified Reynolds number. The friction factor and Nusselt number correlations span the entire range of the data, and agree with the data to within ±20%. In addition, the experimental data of the critical Reynolds number are correlated to within ±10%. The developed correlations are compared to those reported previously. The comparison of the calculated results for a coiled tube and a straight tube, of the same diameter and total length, quantifies the relative heat transfer enhancement and increase in pressure losses. A review of the thermal development in toroidal and coiled tubes indicates that the value and the oscillatory behavior of the local Nusselt number depend on the angular location.