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排序方式: 共有150条查询结果,搜索用时 765 毫秒
51.
52.
An experimental investigation of electrorheological squeeze film dynamics is presented for constant applied voltage and low strain amplitude. Both broadband random and sinusoidal motion are examined to explain complex film dynamics. Spectral results indicate a primarily elastic response with slip at the plate boundaries. By examining the evolution of an effective shear modulus over time, sinusoidal results show that slip at the boundaries is due to a solvent layer which may be modelled as a separate variable thickness squeeze film. 相似文献
53.
Corrigendum: Nickel(II) meso‐Hydroxyporphyrin Complexes Revisited: Palladium‐Catalysed Synthesis,Electronic Structures of Derived Oxy Radicals,and Oxidative Coupling to a Dioxoporphodimethene Dyad 下载免费PDF全文
54.
In this study, the potential for carbonaceous nanomaterials to be used as adsorbents for the mixed matrix membrane (MMM) microextraction and preconcentration of organic pollutants was demonstrated. For this method, multiwall carbon nanotubes (MWCNT) and single layer graphene (SLG) nanoparticles were individually incorporated through dispersion in a cellulose triacetate (CTA) polymer matrix to form a MWCNT-MMM and SLG-MMM, respectively. The prepared membranes were evaluated for the extraction of selected polycyclic aromatic hydrocarbons (PAHs) present in sewage pond water samples. The extraction was performed by dipping a small piece of membrane (7 mm × 7 mm) in a stirred 7.5 mL sample solution to initiate the analyte adsorption. This step was followed by an analyte desorption into 60 μL of methanol prior to high performance liquid chromatography (HPLC) analysis. When the optimum SLG-MMM microextraction technique was applied to spiked sewage pond water samples, the detection limit of the method for the PAHs were in the range of 0.02–0.09 ng/mL, with relative standard deviations of between 1.4% and 7.8%. Enrichment factors of 54–100 were achieved with relative recoveries of 99%–101%. A comparison was also made between the proposed approach and standard solid phase extraction using polymeric bonded octadecyl (C18) cartridges. 相似文献
55.
We present a theoretical model of the behavior of a concentrated electrorheological fluid (ERF) which explicitly takes into account the effects of conductivity. The increase in shear viscosity under an electric field is due to a layered structure between the electrodes, made up of the remnants of particle chains adhering to the electrodes by electrostatic image forces, and a freely flowing liquid layer where all the shear flow is concentrated. This layered model can explain the variation of electric current with shear rate, as well as the rheological response of a dynamic yield stress proportional to the square of the applied electric field. 相似文献
56.
The potential use of plasticized cellulose acetate membranes for electric field driven extraction and preconcentration of inorganic anions was studied. The extraction of highly lipophilic ions such as perchlorate is possible by employing a membrane without any ion carrier, while anions of low lipophilicity, such as phosphate, require a carrier. Best extraction efficiency could be obtained for a membrane of 20 µm thickness and an applied voltage of 200 V. In a flow‐through arrangement the preconcentration factor was inversely dependent on the flow rate but constant for different concentrations. The extraction of perchlorate down to 2 nM was demonstrated. 相似文献
57.
Jung-Ryul Lee See Yenn ChongChang-Yong Yun Dong-Jin Yoon 《Optics and Lasers in Engineering》2011,49(1):110-120
A fiber Bragg grating (FBG) sensor head, using a pressure coupling mechanism, was designed for broadband frequency response and structural strain-free characteristic. The pressure-coupled sensor heads were connected to a simultaneous multipoint acoustic sensing system based on a tunable laser. An intelligent lasing wavelength stabilization algorithm capable of identifying the direction of spectrum movement, the wavelength shifting speed, and a fiber bending event was developed so that the simultaneous multipoint acoustic sensing system could be used in environments with rapid temperature variations. The lasing wavelength feedback control algorithm updated the lasing wavelength into the steep slope of the FBG spectrum even under conditions of rapid temperature change. The averaging lasing wavelength updating time was only 21 s because the system can decide a minimal size in scan window by finding the FBG spectrum shifting speed and direction in real time. The system was able to update the lasing wavelength which missed the steep slope of the FBG spectrum under maximum temperature variation rates 0.3014 and −0.3246 °C/s. The proposed system detected simultaneous impact waves at multiple points under conditions of rapid temperature change and change in dynamic strain. 相似文献
58.
Kosareva O Daigle JF Panov N Wang T Hosseini S Yuan S Roy G Makarov V Chin SL 《Optics letters》2011,36(7):1035-1037
Experimentally measured conical emission rings on the blue side of the filament supercontinuum of a 800 nm 50 fs pulse in air are reproduced in simulations with plasma and the third-order Kerr as the nonlinear terms. This agreement indicates plasma as the dominant mechanism arresting the self-focusing collapse. The higher order Kerr terms with the recently measured coefficients stop the collapse at a lower intensity than the plasma does and lead to the spherical angle-wavelength spectrum without blueshifted rings. 相似文献
59.
A General Palladium‐Catalyzed Method for Alkylation of Heteroarenes Using Secondary and Tertiary Alkyl Halides 下载免费PDF全文
Xiaojin Wu Jessica Wei Ting See Kai Xu Hajime Hirao Julien Roger Jean‐Cyrille Hierso Jianrong Zhou 《Angewandte Chemie (International ed. in English)》2014,53(49):13573-13577
A general alkylation of heterocycles using a simple palladium catalyst is reported. Most classes of heterocycles, including indoles and pyridines, efficiently coupled with unactivated secondary and tertiary alkyl halides. An alkyl radical addition to neutral heteroarenes is most likely involved. 相似文献
60.
Howard See 《Rheologica Acta》2003,42(1-2):86-92
A comparison was made of the behaviour of a magnetorheological suspension under steady shear flow and constant velocity squeezing
flow. The strain rates and sample dimensions were chosen to be comparable in the two deformation modes, and the dependence
of the mechanical properties on the magnetic flux density B was investigated. The measurements found that the mechanical response
under squeezing flow scaled as B0.91, whereas the response under shearing scaled as B1.4, close to theoretical predictions. This difference of the field dependence between the shearing and squeezing flows was possibly
due to the different microstructural rearrangement processes which occur in the two deformation modes. 相似文献