Titanium dioxide (TiO2) nanoparticles were assembled on the surface of nanofiltration blend membrane. For settling TiO2 on the membrane surface, two membrane categories were used: (i) unmodified polyethersulfone (PES)/polyimide (PI) blend membrane, and (ii) –OH functionalized PES/PI blend membrane with different concentrations of diethanolamine (DEA). These membranes were radiated by UV light after TiO2 depositing with different concentrations. 15 min immersion in colloidal suspension and 15 min UV irradiation with 160 W lamps were used for modification. The modification resulted in the formation of a photo-catalytic property with enhanced membrane hydrophilicity. The self-assembly of TiO2 nanoparticles was established through coordinance bonds with –OH functional groups on the membrane surface. A comparison between the UV irradiated TiO2 deposited blend membrane and deposited-functionalized blend membranes showed that –OH groups originate excellent adhesion of TiO2 nanoparticles on the membrane surface, increase reversible deposition, and diminish irreversible fouling. The membranes were characterized using SEM, FTIR, EDX, contact angle, cross flow filtration, and antifouling measurements. SEM images show that the presence of –OH groups on the DEA-modified membrane surface is the main parameter for extra uniformly settlement of TiO2 nanoparticles on the membrane surface. This procedure is a superior technique for modification of PES/PI nanofiltration membranes to enhance water flux and minimization membrane fouling. 相似文献
INTRODUCTION: Image contrast between tissue types can be generated based on their T1/T2 ratio using spin-lock MRI techniques. An interesting application of such a concept would be to generate contrast in tissue with tissue relaxation times modified using exogenous contrast agents. An amplitude-modulated adiabatic waveform has been shown in the past to perform spin-lock MRI. However, implementation of this waveform may not prove to be efficient and practical in research or a clinical setup due to high radiofrequency power deposition. Recent advancement in software and hardware MR technology allows implementation of amplitude- and phase-modulated adiabatic waveforms on MR systems. The aim of this work was to explore role of adiabatic waveforms in performing rho imaging and demonstrate that amplitude- and phase-modulated waveforms [e.g., hyperbolic secant, B1 independent rotation-4 (BIR-4) waveforms] can be used to distinguish materials that differ in T1/T2 ratio. METHODS AND RESULTS: MR simulation was performed using computer routines implemented in MATLAB environment (Mathworks, Natick, MA). Modified Bloch equations with trapezoidal, hyperbolic secant and BIR-4 waveforms were used to perform MR simulation. Trapezoidal waveforms were only used for comparison to other waveforms. Gadolinium DTPA (Gad-DTPA) (T1/T2 approximately 1) and manganese chloride (MnCl(2)) (T1/T2 approximately 10) were used as examples of contrast agents due to their routine use in clinical and research setups and more importantly because they provide good examples of materials differing in T1/T2 ratios. Results of spin locking using trapezoidal waveform agree very well with the previously published results, thereby validating the computer routines used in this MR simulation. Plots of M(rho) (magnetization vector in rho domain) vs. offset frequency show distinct curves for these materials differing in T1/T2 for the three waveforms. BIR-4 waveform demonstrated a 40% difference in M(rho) ( approximately 150 Hz) for the materials. Rate of spin lock with hyperbolic secant waveform was rapid compared to other waveforms. DISCUSSION: MR simulation using contrast agents Gad-DTPA and MnCl(2) provided a useful way to demonstrate that amplitude- and phase-modulated adiabatic waveforms can be used to perform spin-lock imaging. Future work involves implementation of these waveforms on MR scanners and performing in vivo imaging to generate tissue contrast based on relaxation times ratio. 相似文献
In this research in order to predict the strain distribution and extrusion load in equal channel angular extrusion (ECAE) process of circular cross section a new three dimensional kinematically admissible velocity field has been developed based on Bezier formulation. The strain distribution in deformation zone and the effects of various terms on extrusion load were determined. The results were compared both with the experimental and numerically predicted results reported in the literature. It was found that extrusion pressure decreases with increasing both the die angle and the outer curved corner angle and increases with increasing the friction coefficient. Also, it was exhibited that increasing the angle of outer curved corner increases the inhomogeniety of strain field of deformation zone. The predictions were in a good agreement with the FEM and experimental results reported by previous researchers for different die angles and frictional conditions. 相似文献
In this paper, the effects of pure water, SiO2/water nanofluid, and a phase-change material (PCM) as coolants on the performance of a photovoltaic thermal (PVT) system are numerically investigated. The simulations are performed on two modules of PVT with PCM (PVT/PCM module) and without (PVT module). Parameters including PV surface temperature, thermal, and electrical efficiencies of the systems are studied and compared with each other. Moreover, the results of nanofluid as a working fluid is compared with those obtained using pure water. The results show that in the water-based PVT/PCM, the average PV cell temperature is decreased by 16 °C compared to that of the PVT system. This results in an increase of 8% in the electrical efficiency and 25% in the thermal efficiency. In addition, using nanofluid (SiO2 with 1 and 3 mass% mass fraction) as a coolant in the PVT/PCM system increases the thermal efficiency by 3.51% and 10.40%, for 1 and 3 mass%, respectively, compared to that of the PVT/PCM with pure water as a coolant. This study shows that increasing the melting temperature of the phase-change material leads to an increase in the thermal efficiency of the PVT/PCM system.
The structural, electronic, magnetic and vibrational properties of NaZrP, NaZrAs and NaZrSb half-Heusler alloys have been investigated on the basis of density functional theory and generalized gradient approximation. There are three types of structures for these compounds where type a is the most stable one. It is found that all of these materials are half-metallic ferromagnets with a magnetic moment of . The half-metallic gaps are estimated to be 0.16, 0.35 and 0.55 eV for Z = P, As and Sb, respectively. The hybridization between s and orbitals of Zr with s and p orbitals of Z leads to half-metallic ferromagnetism in these compounds. The effect of strain on the half-metallic property is also investigated, and we notice that the half-metallicity is conserved up to the lattice compressions of 54.43%, 48.29% and 47.55% for NaZrP, NaZrAs and NaZrSb, respectively. The dynamical stability of these compounds is confirmed using dispersion curves. The Curie temperatures are also estimated to be 501.29 K, 855.49 K and 1348.88 K for NaZrP, NaZrAs and NaZrSb, respectively. Therefore, it seems that NaZrZ (Z = P, As, Sb) could be suitable materials for spin-injector applications. 相似文献
Cadmium ions react with the collector, ethylhexadecyldimethylammonium bromide (EHDABr), to form a surface-active sublate which can be removed from aqueous bromide
a. Effect of Foreign Metal Ions on the Flotation of Cadmiuma
Foreign ion
Foreign ion concentration (M) (×10?5)
Foreign ion removed (%)
Cadmium removed (%)
None
99.21
Zn2+
6.11
0.06
98.41
Cu2+
6.29
3.64
97.80
Pb2+
3.86
4.80
91.78
Cr6+
7.69
30.75
99.07 solutions by ion flotation. A typical ion flotation procedure involves passing air through a 250-ml solution containing 5 ppm Cd2+, 0.05 M Br?1, and 1.7 × l0?3M EHDABr at a flow rate of 40 ml/min for 1 hr. The procedure was simple and efficient. Chromium, copper, and zinc ions do not interfere under the experimental conditions.
a
Cd2+, 4.46 × 10?5M; EHDABr, 4.25 × 10?4; Br?, 5 × 10?2M; flow rate, 40 ml/min; time, 60 min.
Let R2 be a bounded Lipschitz domain and let
be a Carathèodory integrand such that F(x,·) is polyconvex for L2-a.e. x . Moreover assume thatF is bounded from below and satisfies the condition as det for L2-a.e. x . The paper describes the effect of domain topologyon the existence and multiplicity of strong local minimizersof the functional
wherethe map u lies in the Sobolev space Wid1,p (, R2) with p 2and satisfies the pointwise condition u(x) >0 for L2-a.e.x . The question is settled by establishing that F[·]admits a set of strong local minimizers on that can be indexed by the group Pn Zn, the directsum of Artin's pure braid group on n strings and n copies ofthe infinite cyclic group. The dependence on the domain topologyis through the number of holes n in and the different mechanismsthat give rise to such local minimizers are fully exploitedby this particular representation. 相似文献
In this study, unsteady state one-dimensional heat conduction is analyzed using a polynomial approximation method. As a classical
lumped model is only applicable for use with Biot numbers of less than 0.1, and additionally, it cannot be used for high-temperature
gradients within the region, an improved lumped model is implemented for a typical long slab, long cylinder and sphere. It
has been shown that in comparison to a finite difference solution, the improved model is able to calculate average temperature
as a function of time for higher value of Biot numbers. The comparison also shows that the presented model has better accuracy
when compared with others recently developed models. The simplified relations obtained in this study can be used for engineering
calculations in many conditions. 相似文献
Journal of Thermal Analysis and Calorimetry - A significant amount of the heat is lost in the vehicle exhaust and simply transferred to the environment. Using a thermoelectric generator (TEG), it... 相似文献