基于猴群算法的投影寻踪模型在河流健康评价中的应用

针对现有河流健康评价方法中出现的人为因素影响大、评价结果客观性差等问题,提出了基于猴群算法的投影寻踪河流健康评价模型。该方法可有效避免指标赋权的主观性,克服了一般投影寻踪模型求解方法的缺点。以滦河为例,构建河流健康评价指标体系,进而采用此模型进行评价分析。结果表明,该模型评价结果与实际情况相符,用于河流生态健康评价切实可行;滦河目前处于亚健康状态,在未来几年仍需要加强生态保护,以期达到健康状态。     

基于熵权模糊物元的地下水环境健康评价模型研究

以下辽河平原地下水系统为例,引入模糊物元法并结合熵权和欧氏贴近度理论,构建了基于熵权一模糊物元的地下水环境健康评价模型以综合评价地下水环境健康.结果表明,该法应用于地下水环境健康评价切实可行,直接、客观.     

基于模糊物元模型的干旱等级评价

在建立干旱综合评价指标体系的基础上利用模糊物元和欧氏贴近度理论,构建了基于欧式贴近度的干旱等级评价模糊物元模型并应用于济南市干旱评价研究.结果表明,运用模糊物元模型评价区域干旱状况方法可行、可靠,为评价干旱等级提供了一种考虑多因素的综合方法,具有应用价值和现实意义,可供借鉴.     

基于熵权模糊综合评价模型的桂林市桃花江河流健康评价

为定量评价河流健康现状,在阐述河流健康内涵的基础上构建了河流健康综合评价指标体系,将模糊综合评价法与熵值法相结合,建立了基于熵权的模糊综合评价模型,并将其应用于桂林市桃花江河流健康评价中。结果表明,桃花江上、中、下游的相对隶属度分别为（0.110 31,0.248 77,0.267 29,0.316 90,0.056 73）、（0.143 01,0.191 79,0.413 91,0.204 15,0.047 14）和（0.154 82,0.071 66,0.334 65,0.317 59,0121 28）,其对应的健康级别分别为差、中和中,限制桃花江健康的因素主要有总磷、氨氮、CODcr、鱼类多样性、底栖动物种类、万元GDP用水、供水保证率和防洪能力,研究结果与实际情况相符。     

贝叶斯公式与模糊识别耦合方法在河流健康评价中的应用

为准确评价河流的健康程度,提出了基于贝叶斯公式与模糊识别耦合方法,分析了单个河流健康评价指标属某个等级的概率,用最大似然分类准则判定单个河流健康评价指标的评价等级,引入组合赋权法与相对隶属度综合确定各指标的权重,并将其应用于某市周边6条河流健康评价中。结果表明,除河流Ⅰ的健康评价结果为0.734之外,其他五条河流的评价结果在[0.586,0.628]之间。这表明仅有河流Ⅰ的评价等级为良,河流Ⅱ、Ⅲ、Ⅳ、Ⅴ的评价等级均为中等,河流Ⅵ的的综合评价结果为0.586,评价等级为差,评价结果与实际情况相符。可见基于贝叶斯公式与模糊识别耦合方法合理、可行,不仅提高了河流样本集的权重精确度,且更好地处理了不确定信息。     

基于改进的POME模糊综合评价模型的江苏省河流生态健康评价

为评价江苏省河流生态健康状况,选取反映河流水生境、水生物、社会服务、水管护四个方面的11个评价指标构建评价指标体系,针对传统的基于POME的模糊综合评价模型在权重确定过程中过于主观或完全客观、评价等级确定过程中信息缺失导致结果片面的弊端,利用组合赋权法及加权平均原则加以改进,应用改进后的评价模型评价全省32条骨干河流。发现江苏省河流生态健康综合评判等级值为1.997,整体生态健康状况良好。该模型评价结果与实际情况相符,用于河流生态健康评价切实可行。     

模糊物元模型在水库水质评价中的应用

以燕山水库水质评价为例,针对水质等级的相对模糊性及单项指标评价结果的不相容性问题,基于模糊物元理论,构建了采用三标度法确定权重、将模糊物元分析与欧氏贴近度相结合的水库水质评价模型,并与其他方法进行比较.实例结果表明,评价结果与实际情况相吻合.     

碾压混凝土坝变形监测熵权模糊物元模型研究

基于碾压混凝土坝变形监测的模糊性和单项指标评价结果的不确定性,在运用模糊物元的基础上结合欧氏贴近度概念建立了碾压混凝土坝变形监测的模糊物元模型,并应用信息熵反映数据本身的效用值计算指标的权重系数,避免了权重分配困难和主观判断碾压混凝土坝变形监测的不确定性.实例表明,运用熵权模糊物元模型分析碾压混凝土坝变形状况所得结果与实际情况相符,验证了该方法的有效性.     

基于云物元的混凝土坝裂缝危害性评价模型

针对数据的随机性和等级标准划分模糊的特点,建立了水工混凝土坝裂缝危害性评估的云物元模型,首先依据已有的指标体系和等级评价标准确定相应的云模型参数,采用AHP-熵权法计算评估指标的综合权重;然后以某重力坝为例,计算样本指标属于各评价等级的隶属度,依据最大隶属度原则确定裂缝对坝体结构影响的危害级别。最后将云物元模型与可变模糊模型进行比较,两种模型的评价等级相同,由此证明云物元模型合理、可行,为裂缝的危害性评价提供了一种新方法。     

基于组合权重的模糊物元评价模型在丰县水质评价中的应用

针对传统水质评价模型精度不高的问题,采用熵权法和层次分析法确定权重,并与模糊物元法相结合,建立了基于组合权重的模糊物元评价模型,以江苏省丰县为例,选取全县2012年水功能区监测断面水质监测数据进行水质评价。结果表明,丰县复新河多处水体为Ⅴ类水,郑集河及大沙河多段水体为Ⅳ类水,污染严重,与实际情况基本相符,可见该模型评价结果客观、准确。     

Ash-forming elements in four Scandinavian wood species. Part 1: Summer harvest

Woody biomass in Finland and Sweden comprises mainly four wood species: spruce, pine, birch and aspen. To study the ash, which may cause problems for the combustion device, one tree of each species were cut down and prepared for comparisons with fuel samples. Well-defined samples of wood, bark and foliage were analyzed on 11 ash-forming elements: Si, Al, Fe, Ca, Mg, Mn, Na, K, P, S and Cl. The ash content in the wood tissues (0.2–0.7%) was low compared to the ash content in the bark tissues (1.9–6.4%) and the foliage (2.4–7.7%). The woods’ content of ash-forming elements was consequently low; the highest contents were of Ca (410–1340 ppm) and K (200–1310), followed by Mg (70–290), Mn (15–240) and P (0–350). Present in the wood was also Si (50–190), S (50–200) and Cl (30–110). The bark tissues showed much higher element contents; Ca (4800–19,100 ppm) and K (1600–6400) were the dominating elements, followed by Mg (210–2400), P (210–1200), Mn (110–1100) and S (310–750), but the Cl contents (40–330) were only moderately higher in the bark than in the wood. The young foliage (shoots and deciduous leaves) had the highest K (7100–25,000 ppm), P (1600–5300) and S (1100–2600) contents of all tissues, while the shoots of spruce had the highest Cl contents (820–1360) and its needles the highest Si content (5000–11,300). This paper presented a new approach in fuel characterization: the method excludes the presence of impurities, and focus on different categories of plant tissues. This made it possible to discuss the contents of ash element in a wide spectrum of fuel-types, which are of large importance for the energy production in Finland and Sweden.     

Contents in Volume 23,2014

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Performance assessment of some ice TES systems

In this paper, a performance assessment of four main types of ice storage techniques for space cooling purposes, namely ice slurry systems, ice-on-coil systems (both internal and external melt), and encapsulated ice systems is conducted. A detailed analysis, coupled with a case study based on the literature data, follows. The ice making techniques are compared on the basis of energy and exergy performance criteria including charging, discharging and storage efficiencies, which make up the ice storage and retrieval process. Losses due to heat leakage and irreversibilities from entropy generation are included. A vapor-compression refrigeration cycle with R134a as the working fluid provides the cooling load, while the analysis is performed in both a full storage and partial storage process, with comparisons between these two. In the case of full storage, the energy efficiencies associated with the charging and discharging processes are well over 98% in all cases, while the exergy efficiencies ranged from 46% to 76% for the charging cycle and 18% to 24% for the discharging cycle. For the partial storage systems, all energy and exergy efficiencies were slightly less than that for full storage, due to the increasing effect wall heat leakage has on the decreased storage volume and load. The results show that energy analyses alone do not provide much useful insight into system behavior, since the vast majority of losses in all processes are a result of entropy generation which results from system irreversibilities.     

NEXT GENERATION ENGINEERED MATERIALS FOR ULTRA SUPERCRITICAL STEAM TURBINES

正1 ABSTRACT To reduce the effect of global warming on our climate,the levels of CO2emissions should be reduced.One way to do this is to increase the efficiency of electricity production from fossil fuels.This will in turn reduce the amount of CO2emissions for a given power output.Using US practice for efficiency calculations,then a move from a typical US plant running at 37%efficiency to a 760℃/38.5 MPa(1 400/5 580 psi)plant running at 48%efficiency would reduce CO2emissions by 170kg/MW.hr or 25%.     

Effect of co-cultivation of Chlamydomonas reinhardtii with Azotobacter chroococcum on hydrogen production

Chlamydomonas reinhardtii cc124 and Azotobacter chroococcum bacteria were co-cultured with a series of volume ratios and under a variety of light densities to determine the optimal culture conditions and to investigate the mechanism by which co-cultivation improves H₂ yield. The results demonstrated that the optimal culture conditions for the highest H₂ production of the combined system were a 1:40 vol ratio of bacterial cultures to algal cultures under 200 μE m^?2 s^?1. Under these conditions, the maximal H₂ yield was 255 μmol mg^?1 Chl, which was approximately 15.9-fold of the control. The reasons for the improvement in H₂ yield included decreased O₂ content, enhanced algal growth, and increased H₂ase activity and starch content of the combined system.     

Aerodynamic performance effects of leading-edge geometry in gas-turbine blades

The purpose of this paper is to illustrate the advantages of the direct surface-curvature distribution blade-design method, originally proposed by Korakianitis, for the leading-edge design of turbine blades, and by extension for other types of airfoil shapes. The leading edge shape is critical in the blade design process, and it is quite difficult to completely control with inverse, semi-inverse or other direct-design methods. The blade-design method is briefly reviewed, and then the effort is concentrated on smoothly blending the leading edge shape (circle or ellipse, etc.) with the main part of the blade surface, in a manner that avoids leading-edge flow-disturbance and flow-separation regions. Specifically in the leading edge region we return to the second-order (parabolic) construction line coupled with a revised smoothing equation between the leading-edge shape and the main part of the blade. The Hodson–Dominy blade has been used as an example to show the ability of this blade-design method to remove leading-edge separation bubbles in gas turbine blades and other airfoil shapes that have very sharp changes in curvature near the leading edge. An additional gas turbine blade example has been used to illustrate the ability of this method to design leading edge shapes that avoid leading-edge separation bubbles at off-design conditions. This gas turbine blade example has inlet flow angle 0°, outlet flow angle −64.3°, and tangential lift coefficient 1.045, in a region of parameters where the leading edge shape is critical for the overall blade performance. Computed results at incidences of −10°,   −5°,   +5°,   +10° are used to illustrate the complete removal of leading edge flow-disturbance regions, thus minimizing the possibility of leading-edge separation bubbles, while concurrently minimizing the stagnation pressure drop from inlet to outlet. These results using two difficult example cases of leading edge geometries illustrate the superiority and utility of this blade-design method when compared with other direct or inverse blade-design methods.     

Natural-gas fueled spark-ignition (SI) and compression-ignition (CI) engine performance and emissions

Natural gas is a fossil fuel that has been used and investigated extensively for use in spark-ignition (SI) and compression-ignition (CI) engines. Compared with conventional gasoline engines, SI engines using natural gas can run at higher compression ratios, thus producing higher thermal efficiencies but also increased nitrogen oxide (NO_x) emissions, while producing lower emissions of carbon dioxide (CO₂), unburned hydrocarbons (HC) and carbon monoxide (CO). These engines also produce relatively less power than gasoline-fueled engines because of the convergence of one or more of three factors: a reduction in volumetric efficiency due to natural-gas injection in the intake manifold; the lower stoichiometric fuel/air ratio of natural gas compared to gasoline; and the lower equivalence ratio at which these engines may be run in order to reduce NO_x emissions. High NO_x emissions, especially at high loads, reduce with exhaust gas recirculation (EGR). However, EGR rates above a maximum value result in misfire and erratic engine operation. Hydrogen gas addition increases this EGR threshold significantly. In addition, hydrogen increases the flame speed of the natural gas-hydrogen mixture. Power levels can be increased with supercharging or turbocharging and intercooling. Natural gas is used to power CI engines via the dual-fuel mode, where a high-cetane fuel is injected along with the natural gas in order to provide a source of ignition for the charge. Thermal efficiency levels compared with normal diesel-fueled CI-engine operation are generally maintained with dual-fuel operation, and smoke levels are reduced significantly. At the same time, lower NO_x and CO₂ emissions, as well as higher HC and CO emissions compared with normal CI-engine operation at low and intermediate loads are recorded. These trends are caused by the low charge temperature and increased ignition delay, resulting in low combustion temperatures. Another factor is insufficient penetration and distribution of the pilot fuel in the charge, resulting in a lack of ignition centers. EGR admission at low and intermediate loads increases combustion temperatures, lowering unburned HC and CO emissions. Larger pilot fuel quantities at these load levels and hydrogen gas addition can also help increase combustion efficiency. Power output is lower at certain conditions than diesel-fueled engines, for reasons similar to those affecting power output of SI engines. In both cases the power output can be maintained with direct injection. Overall, natural gas can be used in both engine types; however further refinement and optimization of engines and fuel-injection systems is needed.     

Exergetic evaluation of 5 biowastes-to-biofuels routes via gasification

This paper presents the exergy analysis results for the production of several biofuels, i.e., SNG (synthetic natural gas), methanol, Fischer–Tropsch fuels, hydrogen, as well as heat and electricity, from several biowastes generated in the Dutch province of Friesland, selected as one of the typical European regions. Biowastes have been classified in 5 virtual streams according to their ultimate and proximate analysis. All production chains have been modeled in Aspen Plus in order to analyze their technical performance. The common steps for all the production chains are: pre-treatment, gasification, gas cleaning, water–gas-shift reactions, catalytic reactors, final gas separation and upgrading. Optionally a gas turbine and steam turbines are used to produce heat and electricity from unconverted gas and heat removal, respectively. The results show that, in terms of mass conversion, methanol production seems to be the most efficient process for all the biowastes. SNG synthesis is preferred when exergetic efficiency is the objective parameter, but hydrogen process is more efficient when the performance is analyzed by means of the 1st Law of Thermodynamics. The main exergy losses account for the gasification section, except in the electricity and heat production chain, where the combined cycle is less efficient.     

Controls on the Karaha–Telaga Bodas geothermal reservoir,Indonesia

Karaha–Telaga Bodas is a partially vapor-dominated, fracture-controlled geothermal system located adjacent to Galunggung Volcano in western Java, Indonesia. The geothermal system consists of: (1) a caprock, ranging from several hundred to 1600 m in thickness, and characterized by a steep, conductive temperature gradient and low permeability; (2) an underlying vapor-dominated zone that extends below sea level; and (3) a deep liquid-dominated zone with measured temperatures up to 353 °C. Heat is provided by a tabular granodiorite stock encountered at about 3 km depth. A structural analysis of the geothermal system shows that the effective base of the reservoir is controlled either by the boundary between brittle and ductile deformational regimes or by the closure and collapse of fractures within volcanic rocks located above the brittle/ductile transition. The base of the caprock is determined by the distribution of initially low-permeability lithologies above the reservoir; the extent of pervasive clay alteration that has significantly reduced primary rock permeabilities; the distribution of secondary minerals deposited by descending waters; and, locally, by a downward change from a strike-slip to an extensional stress regime. Fluid-producing zones are controlled by both matrix and fracture permeabilities. High matrix permeabilities are associated with lacustrine, pyroclastic, and epiclastic deposits. Productive fractures are those showing the greatest tendency to slip and dilate under the present-day stress conditions. Although the reservoir appears to be in pressure communication across its length, fluid, and gas chemistries vary laterally, suggesting the presence of isolated convection cells.     

Hydrogen production by steam-gasification of carbonaceous materials using concentrated solar energy – V. Reactor modeling,optimization, and scale-up

A chemical reactor for the steam-gasification of carbonaceous particles (e.g. coal, coke) is considered for using concentrated solar radiation as the energy source of high-temperature process heat. A two-phase reactor model that couples radiative, convective, and conductive heat transfer to the chemical kinetics is applied to optimize the reactor geometrical configuration and operational parameters (feedstock's initial particle size, feeding rates, and solar power input) for maximum reaction extent and solar-to-chemical energy conversion efficiency of a 5 kW prototype reactor and its scale-up to 300 kW. For the 300 kW reactor, complete reaction extent is predicted for an initial feedstock particle size up to 35 μm at residence times of less than 10 s and peak temperatures of 1818 K, yielding high-quality syngas with a calorific content that has been solar-upgraded by 19% over that of the petcoke gasified.