硝酸浓度对橄榄石基活性炭特性的影响(英文)

In this work we investigated the effect of nitric acid concentration on the pore structure, surface chemistry and liquid phase adsorption of olive stone based activated carbon prepared by mixing process using phosphoric acid and steam as activating agents. Chemicals and textural characterization show that the increase of HNO3 concentration increases considerably the total acidic groups but decreases specific surface area and pore volume. The study of adsorption in aqueous solutions of two organics, phenol and methylene blue, on raw and oxidized activated carbon indicates that the treatment of mixed activated carbon with different concentrations of nitric acid improves the adsorbent capacity for methylene blue at HNO3 concentrations less or equal to 2 mol·L 1, while it has a negative effect on phenol adsorption.     

Wireless Sensor Network Based Smart Grid Communications: Challenges,Protocol Optimizations,and Validation Platforms

Wireless Personal Communications - Smart grids, the next generation of electric grids, require the deployment of sophisticated monitoring and control systems to enhance their operational...     

Recent advances on MEMS based Infrared Thermopile detectors

Microsystem Technologies - During the last decade, IR MEMS thermopile detectors have become a topic of increasing interest because of their reliable characteristics and excellent cost-performance...     

Optimization of atrazine removal from synthetic groundwater by electrooxidation process using titanium dioxide and graphite electrodes

ABSTRACT

Atrazine is used in agriculture and is known for its high toxicity. It therefore poses a risk to surface and ground waters, and human life. In this study, an electrochemical method was optimized for atrazine removal from SGW using TiO₂ and graphite electrodes. A comparison between one factor at a time period optimization and Box-Behnken design (BBD) optimization using RSM was carried out to select the optimum conditions. The results show excellent atrazine removal efficiency (99.70%) and close optimum conditions for both applied methods (pH 7 and 7.4; current 2.5 and 2 A and time 14 and 12.12 min, respectively).     

Effect of the Formulation of Sodium Activation Solutions on the Setting Time of Metakaolin Based Geopolymers

Geopolymer materials today represent innovative products,used frequently as a substitute for cementitious traditional materials.They are obtained by the action ...     

Verifying remote data integrity in peer-to-peer data storage: A comprehensive survey of protocols

This paper surveys protocols that verify remote data possession. These protocols have been proposed as a primitive for ensuring the long-term integrity and availability of data stored at remote untrusted hosts. Externalizing data storage to multiple network hosts is becoming widely used in several distributed storage and P2P systems, which urges the need for new solutions that provide security properties for the remote data. Replication techniques cannot ensure on their own data integrity and availability, since they only offer probabilistic guarantees. Moreover, peer dynamics (i.e., peers join and leave at any time) and their potential misbehavior (e.g., free-riding) exacerbate the difficult challenge of securing remote data. To this end, remote data integrity verification protocols have been proposed with the aim to detect faulty and misbehaving storage hosts, in a dynamic and open setting as P2P networks. In this survey, we analyze several of these protocols, compare them with respect to expected security guarantees and discuss their limitations.     

Unexploited Acacia cyanophylla seeds: potential food sources of ω6 fatty acids and antioxidants?

BACKGROUND: In order to investigate new sources of dietary phytochemicals, recent studies have focused on underexploited seeds. In this study the total lipid contents, fatty acid profiles and levels of soluble proteins, minerals and antioxidants in seeds from 12 Acacia cyanophylla ecotypes commonly grown in Tunisia were determined. RESULTS: Total lipids averaged 101.7 g kg^?1 on a dry weight basis. Linoleic (61.11–65.45% of total fatty acid content), oleic (19.67–22.85%) and palmitic (9.18–9.98%) acids were the principal fatty acids. Smaller proportions of stearic (1.49–1.82%), vaccenic (1.13–2.05%) and palmitoleic (0.34–0.58%) acids were also quantified. Proteins (by Kjeldahl assay) averaged 107.2 g kg^?1 on a dry weight basis. Total phenolics averaged 1.91 g gallic acid equivalent kg^?1 dry weight (DW) and total flavonoids averaged 0.40 g rutin equivalent kg^?1 DW. The free radical‐scavenging activity determined by 2,2‐diphenyl‐1‐picrylhydrazyl assay averaged 0.59 mmol L^?1 Trolox equivalent antioxidant capacity (TEAC), while that determined by 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) assay averaged 0.28 mmol L^?1 TEAC. CONCLUSION: The findings of this study confirm the presence of ω6 fatty acids at high levels in A. cyanophylla seeds. These metabolites could be used as such and/or extracted for the formulation of supplements and/or ingredients to provide a ratio close to the ideal for the ω3/ω6 balance. Copyright © 2012 Society of Chemical Industry     

An improved Backstepping technique using sliding mode control for transient stability enhancement and voltage regulation of SMIB power system

The problem of transient stability and voltage regulation for a single machine infinite bus (SMIB) system is addressed in this paper. An improved Backstepping design method for transient stability enhancement and voltage regulation of power systems is discussed beginning with the classical Backstepping to designing the nonlinear excitation control of synchronous generator. Then a more refined version of this technique will be suggested incorporating the sliding mode control to enhance voltage regulation and transient stability. The proposed method is based on a standard third-order model of a synchronous generator connected to the grid (SMIB system). It is basically implemented on the excitation side of the synchronous generator and compared to the classical Backstepping controller as well as the conventional controllers which are the automatic voltage regulator and the power system stabiliser. Simulation results prove the effectiveness of the proposed method which ameliorates to a great extent the transient stability compared to the other methods.     

A high pressure single-pass high-conversion electrochemical cell for intensification of organic electrosynthesis processes

The anode oxidation of 4-methoxytoluene (4-MT) to 4-methoxybenzyl dimethylacetal (4-MBDMA) in methanol is used as a test reaction for the study of a microchannel electrochemical reactor operated continuously in a single-pass high-conversion mode. The cell consists of two stainless steel cathodes, grooved with 100 μm deep channels surrounding a flat glassy carbon anode. Pressures up to 20 bars are applied in the cell in order to reduce the volumetric flow rate of the cathodically produced hydrogen. Both the narrow gap and the operation under pressure lead to an enhancement of the electrolytic conductivity of the cell and make it possible to operate with concentrated solutions, with high current densities and with a very low supporting electrolyte concentration (i.e. 0.01 M KF).The cell performance is discussed in terms of cell voltage, reactant conversion, material and current efficiency and finally selectivity in 4-MBDMA. The effect of inlet reagent concentration, pressure, flow-rate and temperature are investigated. Best performance is obtained with 0.5 M 4-MT at 5 bars and 45 °C: for a 90% conversion, selectivity and current efficiency attain, respectively, 92% and 85%. The high pressure, single-pass high-conversion cell exhibits in this case a space time yield 5–10 times higher than the current industrial process, with a significantly lower concentration of the supporting electrolyte.     

A thin-gap cell for selective oxidation of 4-methylanisole to 4-methoxy-benzaldehyde-dimethylacetal

An electrochemical microreactor for organic electrosynthesis has been investigated for the anodic synthesis of 4-methylanisole to 4-methoxy-benzaldehyde-dimethylacetal in methanol solution. Selectivity and conversion in the single-pass thin-gap flow reactor were examined as a function of the composition of the electrolyte solution, the flow rate and the applied current. The experimental results indicate that potassium fluoride currently used for industrial synthesis and providing higher yields than sodium perchlorate, exerts an influence on the reaction mechanism: high KF concentrations facilitate the undesired oxidation of the diacetal. Nevertheless, a feed solution containing 0.1 M anisole in 0.01 M KF can be converted at 90% in the 100 μm thin-gap cell with acceptable voltages and a measured selectivity of nearly 87%. The selectivity observed substantially higher than that typically observed in conventional electrochemical cells.