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[en] Highlights: • A disturbance rejection solution to the load frequency control issue is proposed. • Several power systems with wind energy conversation system have been tested. • A tuning algorithm of the controller parameters was proposed. • The performance of the proposed approach is better than traditional controllers. - Abstract: A new grid load frequency control approach is proposed for the doubly fed induction generator based wind power plants. The load frequency control issue in a power system is undergoing fundamental changes due to the rapidly growing amount of wind energy conversation system, and concentrating on maintaining generation-load balance and disturbance rejection. The prominent feature of the linear active disturbance rejection control approach is that the total disturbance can be estimated and then eliminated in real time. And thus, it is a feasible solution to deal with the load frequency control issue. In this paper, the application of the linear active disturbance rejection control approach in the load frequency control issue for a complex power system with wind energy conversation system based on doubly fed induction generator is investigated. The load frequency control issue is formulated as a decentralized multi-objective optimization control problem, the solution to which is solved by the hybrid particle swarm optimization technique. To show the effectiveness of the proposed control scheme, the robust performance testing based on Monte-Carlo approach is carried out. The performance superiority of the system with the proposed linear active disturbance rejection control approach over that with the traditional proportional integral and fuzzy-proportional integral-based controllers is validated by the simulation results
[en] Nanoparticles can generate charge carrier trapping and reduce the velocity of streamer development in insulating oils ultimately leading to an enhancement of the breakdown voltage of insulating oils. Vegetable insulating oil-based nanofluids with three sizes of monodispersed Fe_3O_4 nanoparticles were prepared and their trapping depths were measured by thermally stimulated method (TSC). It is found that the nanoparticle surfactant polarization can significantly influence the trapping depth of vegetable insulating oil-based nanofluids. A nanoparticle polarization model considering surfactant polarization was proposed to calculate the trapping depth of the nanofluids at different nanoparticle sizes and surfactant thicknesses. The results show the calculated values of the model are in a fairly good agreement with the experimental values. - Highlights: • Three different sized Fe_3O_4 vegetable-oil based nanofluids was successfully prepared. • The trapping depth of the Fe_3O_4 nanofluids was investigated. • A new model considering surfactant polarization was proposed to calculate the trapping depth of the nanofluids.
[en] Highlights: • ZnO/CuO nanoparticle/dandelion heterostructures were fabricated for the first time. • ZnO/CuO nanoparticle/dandelion heterostructures show enhanced PEC activity. • ZnO nanoparticle loading contents have significant effect on PEC water splitting. • Interaction, charge transfer and enhanced mechanism of photocatalyst were proposed. • p-n junction drives the photoexcited charges efficient separation. - Abstract: Here we report an easy and large-scale synthesis of three-dimensional (3D) ZnO nanoparticle-loaded CuO dandelion (denoted as n-ZnO/p-CuO nanoparticle/dandelion) heterostructures and their photoelectrochemical (PEC) water splitting under simulated solar light illumination. CuO dandelions were fabricated by a facile and cost-effective chemical strategy, in which the ribbon-like CuO nanoplates were first formed and then assembled into dandelion-like architectures. ZnO nanoparticle-loaded CuO dandelion heterostructures were fabricated by calcining Zn(Ac)_2-loaded CuO dandelions. High resolution transmission electron microscope (HRTEM) studies demonstrate that intimate p-n junction is built between p-CuO and n-ZnO interface. The n-ZnO/p-CuO nanoparticle/dandelion photoelectrodes exhibit significant improvement in PEC water splitting to CuO dandelion photoelectrodes. The correlation between photocurrents and different loading contents of ZnO nanoparticles (NPs) is studied in which the n-ZnO/p-CuO nanoparticle/dandelion heterostructures with loading 4.6 wt% ZnO NPs show higher photocathodic current. The efficient separation of the photogenerated electrons and holes driven by the intimate p-n junction between p-type CuO and n-type ZnO interface is mainly contributed to the enhanced photoanode current. The achieved results in the present study offer a very useful strategy for designing p-n junction photoelectrodes for efficiency and low-cost PEC cells for clean solar hydrogen production.
[en] Highlights: • The Mg–Al–CO_3- and magnetic Fe_3O_4/Mg–Al–CO_3–LDH can efficiently remove Cd(II) from aqueous solutions. • The adsorption mechanisms of Cd(II) were discussed in detail. • The adsorption kinetic, isothermal and thermodynamic properties of Cd(II) were studied. • Magnetic Fe_3O_4/Mg–Al–CO_3–LDH can be quickly and easily separated using a magnet. - Abstract: Understanding the adsorption mechanisms of metal cations on the surfaces of solids is important for determining the fate of these metals in water and wastewater treatment. The adsorption kinetic, isothermal, thermodynamic and mechanistic properties of cadmium (Cd(II)) in an aqueous solution containing Mg–Al–CO_3- and magnetic Fe_3O_4/Mg–Al–CO_3-layered double hydroxide (LDH) were studied. The results demonstrated that the adsorption kinetic and isotherm data followed the pseudo-second-order model and the Langmuir equation, respectively. The adsorption process of Cd(II) was feasible, spontaneous and endothermic in nature. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to explain the adsorption mechanisms. The characteristic XRD peaks and FTIR bands of CdCO_3 emerged in the LDH spectra after Cd(II) adsorption, which indicated that the adsorption of Cd(II) by LDHs occurred mainly via CdCO_3 precipitation, surface adsorption and surface complexation. Furthermore, the magnetic Fe_3O_4/Mg–Al–CO_3-LDH can be quickly and easily separated using a magnet before and after the adsorption process.
[en] In this study, a tumor-targeting poly(D, L-lactic-co-glycolic acid) (PLGA) loaded “off-on” fluorescent probe nanoparticle (PFN) delivery system was developed to evaluate the region of tumor by off-on fluorescence. The biodegradability of the nanosize PFN delivery system readily released the probe under tumor acidic conditions. The probe with good biocompatibility was used to monitor the intracellular glutathione (GSH) of cancer cells and selectively localize to mitochondria for tumor imaging. The incorporated tumor-targeting probe was based on the molecular photoinduced electron transfer (PET) mechanism preventing fluorescence (“off” state) and could be easily released under tumor acidic conditions. However, the released tumor-targeting fluorescence probe molecule was selective towards GSH with high selectivity and an ultra-sensitivity for the mitochondria of cancer cells and tissues significantly increasing the probe molecule fluorescence signal (“on” state). The tumor-targeting fluorescence probe showed sensitivity to GSH avoiding interference from cysteine and homocysteine. The PFNs could enable fluorescence-guided cancer imaging during cancer therapy. This work may expand the biological applications of PFNs as a diagnostic reagent, which will be beneficial for fundamental research in tumor imaging.
[en] A new highly sensitive, stable, and accurate fluorometric method for the determination of indium(III) has been established in cetyltrimethylammonium bromide(CTMAB) microemulsion media. The excellent color-forming reagent 2,6,7-trihydroxy-9-(3,5-dibromo-4-hydroxyphenyl)fluorone (DBH-PP) reacts with indium(III) to form a purple complex with a 3 : 1 (ligand to metal) ratio in HAc-NaAc buffer solution at pH 4.94. The emission peak occurs at 556 nm with excitation at 525 nm. Indium(III) can be determined in the linear range of 0.005-0.30 μg ml-1 with a detection limit of 0.0029 μg ml-1. Foreign ions are eliminated by preconcentration and separation with sulfhydryl dextran (SDG). The proposed method has been satisfactorily examined for the determination of indium(III) in ore and sludge samples. The relative standard deviations are in all instances less than 3.0%, and the recoveries are between 94.7% and 99.5%
[ru]Разработан новый высокочувствительный и точный метод флуориметрического определения индия(Ш) в среде микроэмульсии бромида цетилтриметиламмония. Окрашенный реагент 2,6,7-три-гидрокси-9-(3,5-дибром-4-гидроксифенил)флуорон реагирует с индием(Ш) с образованием пурпурного комплекса с соотношением реагент: индий = 3 :1 в ацетатном буферном растворе при рН 4.94. Максимум излучения находится при 556 нм (возбуждение при 525 нм). Можно определять 0.005-0.30 мкг/мл индия с пределом обнаружения 0.0029 мкг/мл. Посторонние ионы удаляют концентрированием и разделением на сульфогидрил-декстрановом геле. Предложенная методика показала удовлетворительные результаты при определении индия в образцах руды и шлама. Относительные стандартные отклонения во всех случаях не превышают 0.030, степени извлечения лежат в интервале 94.7-99.5%
[en] With the rapidly development of the computer network technology and informationize working of our Country, Network and Information Security issues becomes the focal point problem that people shows solicitude for. On the basis analysing security threat and challenge of network information and their developing trend. This paper briefly analyses and discusses the main relatively study direction and content about the theory, technology and practice of Network and Information Security. (authors)
[en] Objective: To study the safety and efficacy of transluminal stent-assisted angioplasty in the treatment of vertebro-basilar ischemia. Methods: Between June 2002 and April 2002, the transluminal stent-assisted angioplasty was performed in 16 patients with symptomatic vertebro-basilar artery stenosis. Results: The vertebral artery stenosis with contralateral stenosis or occlusion were found in 7 patients, unilateral significant stenosis of the dominant vertebral artery in 7, symptomatic basilar artery stenosis in 1, and the significant unilateral lesion of a non-dominant VA. When symptoms indicated ischemia in the ipsilateral posterior cerebellar artery (PICA) in another. The successful rate of stent implantation was 100% without any serious complications. The degree of stenosis was significantly improved from 73.2% to 5.1%, P < 0.01. Within mean follow-up of 4.4 months (ranged from 1 month to 12 months), there was no neurologic complication. Conclusions: Preliminary results suggest that transluminal stent-assisted angioplasty in the treatment of vertebro-basilar ischemia to be a safe and effective. Long-term angiographic and clinical follow-up for monitoring a larger number of patients is needed
[en] Objective: To study the safety and efficacy of endovascular therapy in the treatment of symptomatic intracranial artery stenosis. Methods: The transluminal stent-assisted angioplasty (n=16) or angioplasty (n=3) was performed in 19 patients with symptomatic intracranial artery stenosis. Results: In all patients, Mori type A, B and C lesions were detected in 12, 5 and 2 cases respectively, and the stenotic sites in MCA, ACA, intracranial ICA and intracranial VBA were found in 11, 1, 1 and six respectively. After successful endovascular therapy, the degree of stenosis was significantly improved from 82.9% to 8.0% (P<0.01). There were no serious complications during the peri-procedural period, except one who had Mori type C stenosis of left middle cerebral artery trunk and got complication in SHA 2 hours after successful stent-assisted angioplasty and died 36 hours later. Within mean follow-up of 3.7 months (ranged from 1 month to 9 months), there were no episodes of ischemic neurological events in 18 survivors. Conclusions: Endovascular therapy is effective and feasible for the treatment of symptomatic intracranial artery stenosis. Mori type C lesion should be considered as the contraindication of angioplasty. Larger number of studies are still warranted
[en] Objective: To evaluated the safety and complications of endovascular stenting for symptomatic carotid stenosis with surgical high risk. Methods: A series of 11 vessels in 9 patients at surgical high risk were treated by endovascular stenting. The complications during the procedures and postoperative periods were analyzed within one to five months. Results: All of the operations were successfully performed without any serious complications. During the follow-up period (averaging 6 months), there were no complications of TIAs, stokes and re-stenoses. Conclusions: The study suggests that endovascular stenting may be safe and effective for patients as surgical high risk, but further more study is needed