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Necati Özdemir Author Vitae 《Automatica》2003,39(1):135-140
In this paper we consider integral control algorithms with convergent adaptive sampling for multivariable infinite-dimensional systems. Steady-state gain information is used in choosing suitable integrator gains and we also consider robustness with respect to error in measuring the steady-state gain. 相似文献
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Lokman Uzun Ali Kara Nalan Tüzmen Abdülkerim Karabakan Necati Beirli Adil Denizli 《应用聚合物科学杂志》2006,102(5):4276-4283
We prepared poly(ethylene glycol dimethacrylate–1‐vinyl‐1,2,4‐triazole) [poly(EGDMA–VTAZ)] beads (average diameter = 150–200 μm) by copolymerizing ethylene glycol dimethacrylate (EGDMA) with 1‐vinyl‐1,2,4‐triazole (VTAZ). The copolymer composition was characterized by elemental analysis and found to contain five EGDMA monomer units for each VTAZ monomer unit. The poly(EGDMA–VTAZ) beads had a specific surface area of 65.8 m2/g. Poly(EGDMA–VTAZ) beads were characterized by Fourier transform infrared spectroscopy, elemental analysis, surface area measurements, swelling studies, and scanning electron microscopy. Poly(EGDMA–VTAZ) beads with a swelling ratio of 84% were used for the heavy‐metal removal studies. The adsorption capacities of the beads for Cd(II), Hg(II), and Pb(II) were investigated in aqueous media containing different amounts of these ions (5–750 mg/L) and at different pH values (3.0–7.0). The maximum adsorption capacities of the poly(EGDMA–VTAZ) beads were 85.7 mg/g (0.76 mmol/g) for Cd(II), 134.9 mg/g (0.65 mmol/g) for Pb(II), and 186.5 mg/g (0.93 mmol/g) for Hg(II). The affinity order toward triazole groups on a molar basis was observed as follows: Hg(II) > Cd(II) > Pb(II). pH significantly affected the adsorption capacity of the VTAZ‐incorporated beads. The equilibrium data were well fitted to the Redlich–Peterson isotherm. Consideration of the kinetic data suggested that chemisorption processes could have been the rate‐limiting step in the adsorption process. Regeneration of the chelating‐beads was easily performed with 0.1M HNO3. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4276–4283, 2006 相似文献
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A comparative study of two pre-stressed girder bridges, one with AASHTO (American Association of State Highway and Transportation Officials) Type III girders and the other with new FIB (Florida l-beam) girders, is presented. FIB girders are expected to provide increased lateral stiffness, higher load carrying capacity, cost-efficiency and better reliability. In this paper, the first bridge that is analyzed is a 3-span bridge designed with six AASHTO Type III girders, and the second bridge has four FIB girders with the same span length, width and girder depth. The bridges are analyzed for Florida state legal loads SU4 and C5. Both bridges are analyzed using a sophisticated finite element method. The deflections, moment envelopes, section capacity and live load rating of the two bridges are obtained and compared. FIB girders have higher vertical stiffness, higher section capacity providing higher load rating than the AASHTO girders. 相似文献
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Andria SE Richardson JN Kaval N Zudans I Seliskar CJ Heineman WR 《Analytical chemistry》2004,76(11):3139-3144
We report herein an attenuated total reflectance (ATR) absorbance-based spectroelectrochemical sensor for tris(2,2'-bipyridyl)ruthenium(II) ion [Ru(bpy)(3)(2+)] that employs ultrathin (24-50 nm) Nafion films as the charge-selective layer. This film serves to sequester and preconcentrate the analyte at the optically transparent electrode surface such that it can be efficiently detected optically via electrochemical modulation. Our studies indicate that use of ultrathin films in tandem with continuous flow of sample solution through the cell compartment leads to a 100-500-fold enhancement in detection limit (10 nM) compared to earlier absorbance-based spectroelectrochemical sensors ( approximately 1-5 microM); markedly shorter analysis times also result. We report the dependence of the measured absorbance on sample flow rate and Nafion film thickness, and also provide calibration curves that illustrate the linear range and detection limits of the sensor using a 24 nm film at a constant sample flow rate of 0.07 mL/min. 相似文献
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In order to interpret in detail the experimentally observed current-voltage-temperature (I-V-T) and capacitance-voltage-temperature (C-V-T) results of Al/p-Si metal-semiconductor Schottky barrier diodes (SBDs) we have been examined the samples in the temperature range of 150-375 K. In the calculation method, to confirm the relationship between the I-V-T and C-V-T results, we have reported a modification which includes the ideality factor, n, and tunnelling parameter δχ1/2 in the forward bias current characteristics. In the intermediate bias voltage region (0.1 < V < 0.6 V), the semi-logarithmic plots of the forward I-V-T curves were found to be linear. From the reverse saturation currents I0 obtained by extrapolating the linear region of curves to zero applied voltage, the values of zero bias barrier heights ?B0 were calculated at each temperature. The values of ideality factor calculated from the slope of each curves were plotted as a function of temperature. The values of n are 3.41-1.40 indicating that the Al/p-Si diode does obey the thermionic field emission (TFE) mechanism rather than the other transport mechanism, particularly at low temperature. The high value of ideality factors is attributed to high density of interface states in the SBDs. The temperature dependence energy density distribution profile of interface state was obtained from the forward bias I-V-T measurements by taking into account the bias dependence of the effective barrier height and ideality factor. The interface states density Nss decreasing with increasing temperature was interpreted by the result of atomic restructuring and reordering at the metal-semiconductor interface. After the modification was made to the forward current expression, we obtained a good agreement between the values of barrier height obtained from both methods over a wide temperature. 相似文献
29.
Effect of manufacturing processes on contact resistance characteristics of metallic bipolar plates in PEM fuel cells 总被引:1,自引:0,他引:1
Cabir Turan Ömer Necati Cora Muammer Koç 《International Journal of Hydrogen Energy》2011,36(19):12370-12380
In this study, metallic bipolar plate (BPP) samples manufactured with stamping and hydroforming under different process conditions were tested for their electrical contact resistance characteristics to reveal the effect of manufacturing type and conditions. Punch speed and force in stamping, and pressure and pressure rate in hydroforming were selected as variable process parameters. In addition, two different channel sizes were tested to expose the effect of BPP micro-channel geometry and its consequences on the contact resistance. As a general conclusion, stamped BPPs showed higher contact conductivity than the hydroformed BPPs. Moreover, pressure in hydroforming and geometry had significant effects on the contact resistance behavior of BPPs. Short term corrosion exposure was found to decrease the contact resistance of bipolar plates. Results also indicated that contact resistance values of uncoated stainless steel BPPs are significantly higher than the respective target set by U.S. Department of Energy. Conforming to literature, proper coating or surface treatments are necessary to satisfy the requirements. 相似文献
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Chatterjee S Del Negro AS Edwards MK Bryan SA Kaval N Pantelic N Morris LK Heineman WR Seliskar CJ 《Analytical chemistry》2011,83(5):1766-1772
A spectroelectrochemical sensor consisting of an indium tin oxide (ITO) optically transparent electrode (OTE) coated with a thin film of partially sulfonated polystyrene-blockpoly(ethylene-ran-butylene)-block-polystyrene (SSEBS) was developed for [Tc(dmpe)(3)](+) (dmpe = 1,2-bis(dimethylphosphino)ethane). [Tc(dmpe)(3)](+) was preconcentrated by ion-exchange into the SSEBS film after a 20 min exposure to aqueous [Tc(dmpe)(3)](+) solution, resulting in a 14-fold increase in cathodic peak current compared to a bare OTE. Colorless [Tc(dmpe)(3)](+) was reversibly oxidized to colored [Tc(dmpe)(3)](2+) by cyclic voltammetry. Detection of [Tc(dmpe)(3)](2+) was accomplished through emission spectroscopy by electrochemically oxidizing the complex from nonemissive [Tc(dmpe)(3)](+) to emissive [Tc(dmpe)(3)](2+). The working principle of the sensor consisted of electrochemically cycling between nonemissive [Tc(dmpe)(3)](+) and emissive [Tc(dmpe)(3)](2+) and monitoring the modulated emission (λ(exc) = 532 nm; λ(em) = 660 nm). The sensor gave a linear response over the concentration range of 0.16-340.0 μM of [Tc(dmpe)(3)](2+/+) in aqueous phase with a detection limit of 24 nM. 相似文献