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排序方式: 共有241条查询结果,搜索用时 31 毫秒
21.
S Naderi 《Canadian Metallurgical Quarterly》1976,7(1):133-139
The dimerization of the variable fragment of the Bence-Jones protein Au was examined in phosphate buffers at pH 6.8-6.9 And ionic strength of 0.1 M or 0.2 M at 20 degrees C. The dimerization constant was about 1 X 10(5) M-1. The reaction enthalpy was positive and the process was entropy driven. The association and dissociation rate constants were 9 X 10(6) M-1 s-1 and 1.5 X 10(2) s-1 respectively. Temperature-jump experiments exhibited the presence of two isomers of the dimer, which are present at equilibrium in a ratio of about 1:1. Isomerization occurred with a half-life of about 0.1 s. 相似文献
22.
The thermal conductivity of a metal, subjected to cyclic loading, changes as it degrades due to the appearance of micro-cracks
and micro-voids. This continues up to the critical stage where macro-cracks are created and failure occurs. In this study,
a theoretical model for thermal-conductivity deterioration is presented that accounts for the cyclic loading. To examine the
validity of the results obtained from a theoretical model, an apparatus is designed to measure thermal-conductivity degradation
by means of the guarded-comparative-longitudinal heat-flow technique. Results of a series of thermal-conductivity measurements
at several stages of torsional fatigue tests are presented. It is shown that the thermal conductivity of Al 6061-T6 decreases
approximately 8 % to 12 % before complete failure takes place. 相似文献
23.
R. Naderi 《Electrochimica acta》2009,54(27):6892-8733
This work intends to study inhibitive performance of organic and inorganic complexes of Zn(II) using electrochemical techniques along with surface analysis. In this regard, inorganic zinc aluminum polyphosphate pigment as modified zinc phosphate and zinc acetylacetonate and benzimidazole mixture representing organic replacement of zinc phosphate were employed. Through taking advantage of electrochemical impedance spectroscopy and DC polarization, two mentioned approaches were indicated to be efficient. Charge transfer resistance and corrosion current density values exhibited superiority of zinc aluminum polyphosphate and mixture of zinc acetylacetonate and benzimidazole compared to zinc phosphate and also zinc acetylacetonate and benzimidazole as individual inhibitors. Corrosion inhibition efficiencies calculated based on charge transfer resistance in consistent with those calculated from corrosion current density showed the following sequence; zinc aluminum polyphosphate > mixture of zinc acetylacetonate and benzimidazole > zinc acetylacetonate > zinc phosphate > benzimidazole. Showing film formation, surface analysis SEM/EDX confirmed the results obtained by electrochemical methods. 相似文献
24.
Evaluation of the effect of vinyltrimethoxysilane on corrosion resistance and adhesion strength of epoxy coated AA1050 总被引:2,自引:0,他引:2
The quality of surface treatment of aluminum alloy (AA1050) with vinyltrimethoxysilane (VTMS) was examined. Calculated surface energy with Van Oss, Chaudury and Good (VOCG) method showed higher surface energy of treated specimens. Chemical interaction between silane layer and aluminium surface was examined via FTIR-ATR. In addition, practical adhesion was measured in dry, wet and recovered states via pull-off method and compared to adhesion strength of desmutted and chromated specimens. Results showed good adhesion performance in dry state for silane treated specimens. Corrosion protective performance of epoxy coating in the presence of silane layer on aluminum was studied with Electrochemical Impedance Spectroscopy (EIS) and compared with coated desmutted and chromated specimens. Water sensitivity of silane layer resulted in poor protective performance of specimens treated at pH > isoelectric point (IEP). 相似文献
25.
Supertough (Polyamide 6)/(acrylonitrile butadiene rubber) nano alloy through in situ polymerization of caprolactam in the presence of acrylonitrile butadiene rubber nanophase 下载免费PDF全文
Shervin Ahmadi Yousef Jahani Ghasem Naderi Amir Hossein Asadollahzadeh 《乙烯基与添加剂工艺杂志》2015,21(2):116-121
In this work, polymerization of caprolactam (CL) was carried out in the presence of acrylonitrile butadiene rubber (NBR) during the reactive melt‐mixing process. During shear mixing, NBR particles swelled and dissolved in the molten CL, which led to separation and distribution of rubber particles to nanoscale in the dissolution stage. Then, in an internal mixer, supertough Polyamide 6 was prepared via melt polymerization of CL/NBR mixture, sodium caprolactam as a catalyst, and hexamethylene diisocyanate as an activator. The effects of various concentrations of catalyst and activator on the initiation time of the reaction were determined. Physical and mechanical properties of different formulations prepared via reactive melt blending were determined by tensile and impact measurements, differential scanning calorimetry, Fourier‐transform infrared spectroscopy, X‐ray scattering techniques, transmission electron microscopy, and dynamic mechanical thermal analysis. Experimental results showed that a recipe with 3% nitrile rubber in a CL/NBR mixture enhances the physical and mechanical properties the best, compared with other formulations. This condition led to the formation of NBR nanospheres during melt polymerization of Polyamide 6 as well. J. VINYL ADDIT. TECHNOL., 21:116–121, 2015. © 2014 Society of Plastics Engineers 相似文献
26.
Mahdi Delaviz Bayekolaei Koorosh Naderi Fereidoon Moghadas Nejad 《Petroleum Science and Technology》2016,34(16):1439-1446
This study aimed to characterize the rate of change that takes place in the mechanical properties of polymer-nanocomposite asphalt (PNMA) mixtures due to altering asphalt binder grade and styrene-butadiene-styrene (SBS) type. Laboratory testing program included Marshall stability, resilient modulus, and wheel-tracking tests. Test results were compared and analyzed statistically by means of two-way analysis of variance and Tukey test. Variance analysis indicated the significant effect of both binder type and SBS grade on mechanical properties of asphalt mixtures. Interaction between binder type and SBS grade is also meaningful in all the experiments. The results also show that the binder type is the primary affecting factor, followed by the SBS grade. 相似文献
27.
In this article, an exact analytical solution for buckling analysis of moderately thick functionally graded (FG) sector plates resting on Winkler elastic foundation is presented. The equilibrium equations are derived according to the first order shear deformation plate theory. Because of the coupling between the bending and stretching equilibrium equations of FG plates, these plates have deflection under in-plane loads lower than the critical buckling load acting on the mid-plane. The conditions under which FG plates remain flat in the pre-buckling configuration are investigated and the stability equations are obtained based on the flat plate assumption in the pre-buckling state. The stability equations are simplified into decoupled equations and solved analytically for plates having simply supported boundary condition on the straight edges. The critical buckling load is obtained and the effects of geometrical parameters and power law index on the stability of functionally graded sector plates are studded. The results for the critical buckling load of moderately thick functionally graded sector plates resting on elastic foundation are reported for the first time. 相似文献
28.
Prediction of geological hazardous zones in front of a tunnel face using TSP-203 and artificial neural networks 总被引:3,自引:0,他引:3
Andisheh Alimoradi Ali Moradzadeh Reza Naderi Mojtaba Zad Salehi Afshin Etemadi 《Tunnelling and Underground Space Technology incorporating Trenchless Technology Research》2008,23(6):711-717
This research aims at improving the methods of prediction of hazardous geotechnical structures in the front of a tunnel face. We propose and showcase our methodology using a case study on a water supply system in Cheshmeh Roozieh, Iran. Geotechnical investigations had previously reported three measurements of the newly established method of TSP-203 (Tunnel Seismic Prediction) along 684 m of the 3200 m long tunnel up to a depth of 600 m. We use the results of TSP-203 in a trained artificial neural network (ANN) to estimate the unknown nonlinear relationships between TSP-203 results and those obtained by the methods of Rock Mass Rating classification (RMR – treated here as real values). Our results show that an appropriately trained neural network can reliably predict the weak geological zones in front of a tunnel face accurately. 相似文献
29.
S Naderi S Ozgen MN Pamir MM Ozek C Erzen 《Canadian Metallurgical Quarterly》1998,43(1):43-9; discussion 49-50
OBJECTIVE: A variety of factors may affect surgical outcome in patients with cervical spondylotic myelopathy. The aim of this study is to determine these factors on the basis of preoperative radiological and clinical data. METHODS: To assess the factors affecting postoperative outcome after surgery for cervical spondylotic myelopathy, the clinical and radiological data of 27 patients with cervical spondylotic myelopathy were reviewed. Functional and neurological statuses were assessed using the Japanese Orthopaedic Association (JOA) scale modified by Benzel. In all patients, the effect of age, symptom duration, cervical curvature, presence or absence of preoperative high signal intensity within the spinal cord as revealed by T2-weighted magnetic resonance imaging, and diameters of the spinal canal and vertebral body on pre- and postoperative neurological statuses were investigated. Plain radiographs were obtained for all patients, magnetic resonance images for 21 patients (77.8%), computed tomographic scans for 13 patients (48.1%), myelograms for 6 patients (22.2%), and computed tomographic myelograms for 4 patients (14.8%). There were five patients with a JOA score of 10, six patients with a JOA score of 11, six patients with a JOA score of 12, four patients with a JOA score of 13, four patients with a JOA score of 14, one patient with a JOA score of 15, and one patient with a JOA score of 16. All patients underwent cervical laminectomies. The mean follow-up period was 54.1 months. The final neurological examinations revealed improvement in the JOA scores of 85.1 % of the patients. RESULTS: Statistical analysis of all patients revealed mean JOA scores of 12.185 +/- 1.618 and 14.370 +/- 2.15 before surgery and at final examination, respectively. The difference between the preoperative JOA score and the final JOA score was determined to be statistically significant (P < 0.0001). Statistical analyses also showed better neurological improvement in patients younger than 60 years and in patients with normal preoperative cervical lordosis. Although patients without preoperative high signal intensity of the spinal cord showed a better improvement rate than did patients with preoperative high signal intensity, the determined difference was statistically insignificant. CONCLUSION: It can be concluded that age and abnormal cervical curvature predict less postoperative neurological improvement. The presence of preoperative high signal intensity within the spinal cord may also reflect less neurological improvement. 相似文献
30.
Electrochemical impedance spectroscopy was employed to evaluate protective performance of the solvent-borne epoxy coatings pigmented with zinc aluminum polyphosphate as a representative of phosphate-based anticorrosion compounds at different Lambda values. Furthermore, the effective ratio of the pigment volume concentration (PVC) to the critical pigment volume concentration (CPVC) was determined. To compare the function of zinc aluminum polyphosphate and zinc phosphate incorporated into coatings, electrochemical noise method as well as electrochemical impedance spectroscopy was taken into consideration. The trend and magnitude of charge transfer, coating and noise resistances plus the amplitude of the current noise fluctuation indicated superiority of the modified pigment. In order to provide an insight into the mechanism by which anticorrosion pigments improve protective behavior of coating, performance of bare metals exposed to pigment extracts was assessed through taking advantage of electrochemical impedance spectroscopy and electrochemical noise method as well. 相似文献