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181.
Dora Nava 《Electrochimica acta》2006,51(25):5295-5303
The dissolution mechanism of chalcopyrite, and the potential range in which its passivation phenomenon takes place, were studied on carbon paste electrodes with chalcopyrite (99.46% purity, +300 mesh, 53 μm size) (CPE-CP) in 1.7 mol/dm3 H2SO4. A sequence of anodic potential pulses was applied to the CPE-CP to characterize its electrochemical behavior. Copper ions, dissolved by the potential pulses, were determined using a mercury film electrode (MFE) and the anodic stripping voltammetry (ASV) on a vitreous carbon disk. In addition, the modified surface of CPE-CP was characterized, before and after the potential pulses, by cyclic voltammetry (CV). The characterization of the final surface state of each electrochemically modified CPE-CP and the amount of dissolved copper showed five potential regions where the chalcopyrite dissolution mechanism changed. The initial dissolution occurs at 0.615 V ≤ Eanod < 1.015 V versus SHE forming a non-stoichiometric polysulfide (Cu1−rFe1−sS2−t). The absence of copper ions in the solution indicates a passive sulfide. However, at 1.015 V ≤ Eanod < 1.085 V versus SHE, the passive product decomposes forming porous layers of non-stoichiometric polysulfide (Cu1−xFe1−yS2−z) that allow the diffusional transport of charged species and the dissolution of the mineral. In the region of 1.085 V ≤ Eanod < 1.165 V versus SHE, formation covellite (CuS) was identified. At E > 1.165 V versus SHE, CuS is unstable and gives rise to complete dissolution of the chalcopyrite. Due to the experimental conditions, the mineral dissolution is inhibited by possible jarosite precipitation. 相似文献
182.
协调经济性及电压稳定性的受端系统紧急负荷控制优化方法 总被引:1,自引:0,他引:1
特高压直流逆变站闭锁后,应在确保受端系统安全稳定的前提下尽量减小紧急控制的经济代价,同时,为了使逆变器尽快恢复正常运行,控制后的系统还需要提供足够的无功支撑,为此提出了一种协调经济性及电压稳定性的受端系统紧急负荷控制优化方法。首先,讨论了事故发生后受端系统的动态响应,提出根据电压薄弱性指标识别受端系统的若干电压薄弱节点,将其电压跌落量的平方和作为电压稳定性指标;然后,计算控制方案对应的负荷损失及事故罚款,将两者之和作为经济指标。为克服分段优化问题的求解困难,首先将分段的事故罚款曲线进行了近似光滑处理;然后,在考虑频率、电压及潮流等约束条件的基础上,以经济性、电压稳定性指标的加权和最小为目标,构建紧急负荷控制优化问题的数学模型,并应用原对偶内点法快速求解;最后,以含高压直流输电的IEEE 10机39节点系统为例,对算法进行了验证。结果表明,协调经济性及电压稳定性的优化控制可在不增加经济代价的前提下,改善控制后系统的电压稳定性,有助于逆变站恢复运行。 相似文献
183.
Romain Blanc Paola Nava Michel Rajzman Laurent Commeiras Jean‐Luc Parrain 《Advanced Synthesis \u0026amp; Catalysis》2012,354(10):2038-2048
An update of our preliminary communication concerning an efficient organocatalytic procedure for the transfer of tin onto aldehydes is presented. This update combines (i) a full study of the preparation of γ‐silyloxyallylstannanes from β‐substituted enals, (ii) a “one‐pot” sequence (in inter‐ and intramolecular version) including N‐heterocyclic carbene (NHC)‐catalyzed silylstannation reaction/Lewis acid‐promoted allylstannation reaction to furnish the corresponding syn‐diols, and (iii) mechanistic studies on the organocatalytic 1,2‐addition. 相似文献
184.
185.
电网调度省地一体化试点工程关键技术方案 总被引:1,自引:0,他引:1
为适应电网智能化发展的进一步要求,省地电力调度控制中心(简称省地调)基于全景信息进行电网一体化运行和统一协调控制成为迫在眉睫的需求。文中针对电网模型、采集数据、功能应用等方面对电网调度省地一体化关键技术开展研究,实现省地调之间电网模型、图形等信息能够动态交互和按需共享,实时数据、历史数据、故障信息等信息能够动态交互、按需引用和校核互备,并探索实现若干省地一体化典型应用。该研究课题也是智能电网调度技术支持系统在江苏试点工程建设的重点内容。 相似文献
186.
F. Amato S. Nava X. Querol J.M. Baldasano M. Pandolfi 《The Science of the total environment》2010,408(20):4309-9997
Compliance with air quality standards requires control of source emissions: fine exhaust particles are already subject to regulation but vehicle fleets increase whilst the non-exhaust emissions are totally uncontrolled. Emission inventories are scarce despite their suitability for researchers and regulating agencies for managing air quality and PM reduction measures. Only few countries in Europe proposed street cleaning as a possible control measure, but its effectiveness is still far to be determined.This study offers first estimates of Real-world Emission Factors for PM10 and brake-wear elements and the effect on PM10 concentrations induced by intense street cleaning trials.A straightforward campaign was carried out in the city of Barcelona with hourly elemental composition of fine and coarse PM to detect any short-term effect of street cleaning on specific tracers of non-exhaust emissions. Samples were analyzed by Particle Induced X-Ray Emission.Real-world Emission Factor for PM10 averaged for the local fleet resulted to be 97 mg veh− 1 km− 1. When compared to other European studies, our EF resulted higher than what found in UK, Germany, Switzerland and Austria but lower than Scandinavian countries. For brake-related elements, total EFs were estimated, accounting for the sum of direct and resuspension emissions, in 7400, 486, 106 and 86 μg veh− 1 km− 1, respectively for Fe, Cu, Sn and Sb. In PM2.5Fe and Cu emission factors were respectively 4884 and 306 μg veh− 1 km− 1.Intense street cleaning trials evidenced a PM10 reduction at kerbside of 3 μg m− 3 (mean daily levels of 54 μg m− 3), with respect to reference stations. It is important to remark that such benefit could only be detected in small time-integration periods (12:00-18:00) since in daily values this benefit was not noticed. Hourly PM elemental monitoring allowed the identification of mineral and brake-related metallic particles as those responsible of the PM10 reduction. 相似文献
187.
Physicochemical characterization of sludge obtained from refined hydrocarbons transmission pipeline was carried out through Mössbauer spectroscopy and X-ray diffraction. The Mössbauer and X-ray patterns indicate the presence of corrosion products composed of different iron oxide and sulfide phases. Hematite (α-Fe2O3), magnetite (Fe3O4), maghemite (γ-Fe2O3), magnetic and superparamagnetic goethite (α-FeOOH), pyrrhotite (Fe1−xS), akaganeite (β-FeOOH), and lepidocrocite (γ-FeOOH) were identified as corrosion products in samples obtained from pipeline transporting Magna and Premium gasoline. For diesel transmission pipeline, hematite, magnetite, and magnetic goethite were identified. Corrosion products follow a simple reaction mechanism of steel dissolution in aerated aqueous media at a near-neutral pH. Chemical composition of the corrosion products depends on H2O and sulfur inherent in fluids (traces). These results can be useful for decision-making with regard to pipeline corrosion control. 相似文献
188.
In this paper we report the viability of using porous silicon photonic mirrors (PSPM) as secondary reflectors in solar concentration systems. The PSPM were fabricated with nanostructured porous silicon to reflect light from the visible range to the near infrared region (500-2500 nm), although this range could be tuned for specific wavelength applications. Our PSPM are multilayers of two alternated refractive indexes (1.5 and 2.0), where the condition of a quarter wavelength in the optical path was imposed. The PSPM were exposed to high radiation in a solar concentrator equipment. As a result, we observed a significant degradation of the mirrors at an approximated temperature of . In order to analyze the origin of the degradation of PSPM, we model the samples with a non-linear optical approach and study the effect of a temperature increase. Those theoretical and experimental studies allow us to conclude that the main phenomenon involved in the breakdown of the photonic mirrors is of thermal origin, produced by heterogeneous expansion of each layer. Our next step was to introduce a cooling system into the solar concentrator to keep the mirrors at approximately , with very good results. As a conclusion we propose the use of PSPM as selective secondary mirrors in solar concentration devices using temperature control to avoid thermal degradation. 相似文献
189.
190.
红外热成像信号处理技术的研究进展 总被引:1,自引:0,他引:1
红外热成像技术通过二维图像的形式准确反映物体表面温度分布情况,广泛应用于医疗诊断、故障检测、能耗监控及智能驾驶等众多工业领域。针对制约红外热成像技术发展的3个主要瓶颈问题,分别阐述相关研究领域内最新的科研进展。首先,介绍红外信号固定模式噪声建模及除噪方法,解决信号采集系统中关键部件焦平面阵列传感器存在的严重噪声干扰;其次,介绍红外信号特征重建理论的研究,克服红外焦平面阵列探测器制作工艺复杂、成品率低及价格昂贵等制约了红外热成像技术广泛工业应用的问题;最后,探索多源信息融合技术,减少二维图像采集过程中降维映射导致的信息损失,提高基于多光谱信息进行目标检测系统的性能。红外热成像信号处理技术的最新科研进展,为新一代高成像精度、高分辨率、低制作成本的三维红外成像仪器的研发提供新理论与技术。 相似文献