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排序方式: 共有56条查询结果,搜索用时 15 毫秒
1.
Al-MCM-41 molecular sieves with Si/Al ratios 25, 50, 75 & 100 were synthesized hydrothermally and characterized systematically
by various analytical and spectroscopy techniques. Their catalytic activity was evaluated for the vapour phase reaction of
butyric acid with 1-pentanol. Pentyl butyrate was obtained as the only product. Reaction parameters such as temperature, molar
ratio and feed rate were optimized for higher butyric acid conversion. The time-on-stream study was carried out at optimum
conditions resulting in gradual decrease in the activity of the catalyst. 相似文献
2.
A technique that is sensitive to change in texture is more reliable than mechanical property measurements for the study of
recrystallization behavior in alloys where recrystallization is coupled with precipitation. Hence, ultrasonic velocity measurements
have been employed to characterize microstructural changes during annealing of cold worked Ti-modified austenitic stainless
steel where precipitation of TiC is known to retard recrystallization. Mechanical property measurements, such as strength
and hardness, could not distinguish the recovery and recrystallization regimes, and it was difficult to determine the exact
time or temperature for onset of recrystallization. The variation of velocity with annealing time or annealing temperature
exhibited a three-stage behavior. The velocity exhibited a slight increase in the recovery region followed by a sharp and
continuous decrease in the recrystallization region and reached saturation on completion of recrystallization. Based on the
microstructural investigations, the three stages were identified to be recovery, progress of recrystallization, and completion
of recrystallization. Velocity measurements could sense the onset, progress, and completion of recrystallization more accurately
compared with that of hardness and strength measurements. 相似文献
3.
Jin-Soo Park Palanichamy Krishnan Seok-Hee ParkGu-Gon Park Tae-Hyun YangWon-Yong Lee Chang-Soo Kim 《Journal of power sources》2008
The porosity effect of catalyst electrodes in membrane-electrode assemblies (MEAs) using a hydrocarbon-based polymer as electrolyte and ionomer was investigated on physical and electrochemical properties by varying the content of ionomer binder (dry condition) in the catalyst electrodes. The MEAs were compared with the Nafion®-based MEA using Nafion® 112 and 5 wt.% ionomer solution (EW = 1100) in terms of porosity values, scanning electron microscopic images, Nyquist plots, dielectric spectra and I–V polarization curves. In this study, sulfonated poly(ether ether ketone) (SPEEK) membranes with 25 ± 5 μm of thickness and 5 wt.% ionomer solutions have been prepared. The prepared membranes were characterized in terms of FT-IR, DSC and proton conductivity. Proton conductivity of the SPEEK membranes was compared with one of the Nafion® membranes with relative humidity. The porosity of the catalyst electrodes was calculated using the properties of catalyst, ionomer solution and solvent. As a result, the performance of the new type polymer (i.e., SPEEK in this study)-based MEA with the similar membrane conductivity and porosity of the catalyst electrode in the Nafion® MEA was similar to that of the Nafion® MEA. 相似文献
4.
Palanichamy Esakkiraj Rajamony Usha Arunachalam Palavesam Grasian Immanuel 《Food and Bioproducts Processing》2012,90(3):370-376
The bacterium Bacillus altitudinis AP-MSU, able to produce esterase was isolated from the gut of marine fish Sardinella longiceps. The esterase production was investigated in solid-state fermentation experiment using various fish processing waste meal. Among the tested fish processing wastes, red grouper waste emerged as the best source for higher esterase production. The suitable surfactant and triglyceride identified to increase the lipase production was neem oil. Effect of individual carbon and nitrogen sources supplementation on esterase production revealed that fructose and peptone aided the higher esterase production than the other tested carbon and nitrogen sources. The suitable concentration of sodium chloride for higher esterase production was at 5%. Effect of surfactants and trace elements on esterase production showed that Tween 20 and zinc sulphate, respectively produced maximum amount of esterase. The effect of physical parameters on lipase production revealed that 50 °C temperature and pH 7–8 were optimum for higher esterase production. Statistical optimization with Plackett–Burman design showed that neem oil, NaCl and fructose were found to be the most predictive factors for esterase production by this strain. 相似文献
5.
Mahalakshmi M Arabindoo B Palanichamy M Murugesan V 《Journal of hazardous materials》2007,143(1-2):240-245
The photocatalytic degradation of carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate) was investigated in an aqueous solution using Degussa P-25 TiO2 and ZnO as photocatalysts. The progress of degradation was monitored using TOC analyzer, HPLC, GC-MS and UV-vis spectrophotometer. The effects of various experimental parameters such as initial concentration of carbofuran, pH of the solution, catalyst loading and light intensity were systematically studied in order to achieve maximum degradation efficiency. The complete mineralization of carbofuran was confirmed by TOC analyzer. The degradation with ZnO showed less efficiency than TiO2. The formation of NO(3)(-) was identified and quantified using HPLC. In addition, four different intermediates formed during the degradation process were also identified and characterized by GC-MS. The mineralization rate was compared with lamps of wavelength 254 and 365 nm under similar conditions. The rate with 254 nm was observed to be very close to that of 365 nm. 相似文献
6.
P. Shankar P. Palanichamy T. Jayakumar Baldev Raj S. Ranganathan 《Metallurgical and Materials Transactions A》2001,32(12):2959-2968
The presence of even dilute concentrations of nitrogen (0.08 mass pct) is found to have a strong influence on the microstructure
of a nuclear grade 316LN austenitic stainless steel, thermally aged at 1123 K. High-resolution transmission electron microscopy
(TEM) evidence of pre-precipitation reactions involving formation of Cr-N rich clusters prior to Cr2N precipitation has been presented. A tendency for cellular precipitation has been observed on continued aging above 500 hours.
Beyond 1000 hours, chi precipitates are the most frequently seen phase. The observed microstructural variations correlate
well with ultrasonic velocity and attenuation measurements. The present study reveals that nitrogen in solid solution decreases
all the elastic constants, namely longitudinal modulus, elastic modulus, shear modulus, and bulk modulus in this steel but
has a negligible effect on Poisson’s ratio. The stages associated with the precipitation of intragranular coherent Cr2N are, however, associated with an increase in all the elastic constants including Poisson’s ratio. 相似文献
7.
Precise measurements of shear wave velocities have been made in 20% cold worked and annealed samples of alloy D9 (Ti-modified austenitic stainless steel) to characterize the microstructural changes during annealing. The variation in wave velocity with annealing time exhibited a three stage behaviour. In the first stage, a slight increase in the velocity during recovery regime has been observed. This is followed by a significant increase in the velocity in the recrystallization regime (second stage) and reaching saturation on completion of recrystallization (third stage). Microstructural observations using optical metallography confirmed these three stages. The maximum variation in velocity is observed only when the polarization or the propagation direction of the shear wave is alingned with the cold working direction. Variation in shear wave velocity during annealing process, in general, is just opposite to that of the variation in longitudinal wave velocity. A number of velocity measurements were made by changing the propagation and polarization directions of the shear waves with respect to the cold working direction. Based on these measurements, a suitable velocity ratio parameter is suggested for determining the degree of recrystallization during annealing of cold worked alloy D9. 相似文献
8.
S. Maria Rayappan D. Easwaramurthy M. Palanichamy V. Murugesan 《Inorganic chemistry communications》2010,13(1):131-133
Silver(I) catalyzed oxidation of amino acids such as glycine and α-alanine by peroxomonosulphate (PMS) in aqueous perchloric acid medium was found to be first order in [peroxomonosulphate] and fractional order in [amino acid] and [Ag(I)]. The rate equation was derived by assuming equilibrium formation of adduct between amino acids and Ag(I). This adduct was presumed to react with PMS in a slow step to yield (adduct)2+, which was self-oxidized in a fast step to give the products. The kinetic results revealed that silver catalyzed reaction occurred approximately 104 times faster than the uncatalyzed reaction and this is attributed to the formation of (adduct)2+. The bimolecular rate constant (k) for the slow step and the activation parameters were calculated and the results are discussed. 相似文献
9.
S. Sudha S. Vishnu Priya J. Herbert Mabel M. Palanichamy V. Murugesan 《Journal of Porous Materials》2009,16(2):215-226
Al-MCM-41, Fe,Al-MCM-41 and Zn,Al-MCM-41 materials with different silicon to metal ratios were synthesized hydrothermally
and characterized by XRD, BET, FT-IR, Acidity measurement by pyridine adsorbed FT-IR spectroscopy, 29Si and 27Al MAS NMR and ESR techniques. The orderly arrangement of mesoporous materials was clearly revealed from the XRD patterns.
29Si and 27Al MAS NMR established the co-ordination environment of silicon and aluminium. Electron paramagnetic resonance (EPR) study
confirmed the co-ordination environment of Fe in Fe,Al-MCM-41 framework. The catalytic activity of these materials was evaluated
in the vapour phase alkylation and acylation of ethylbenzene with ethyl acetate in the temperature range between 250 and 400 °C.
The products were found to be 1,3-diethylbenzene (1,3-DEB), 1,4-diethylbenzene (1,4-DEB), 1,2-diethylbenzene (1,2-DEB), 4-ethylacetophenone
(4-EAP) and acetophenone (AP). The reaction products revealed that activation of ethyl acetate is a convenient route for both
alkylation and acylation reactions. The order of the catalysts activity for the reaction is found to be Fe,Al-MCM-41 (50) > Fe,Al-MCM-41
(100) > Zn,Al-MCM-41 (50) > Zn,Al-MCM-41 (100) > Al-MCM-41 (50) > Al-MCM-41 (100). In addition to the density of acid sites,
the strength of acid sites is also important for this reaction. The effects of temperature, feed ratio, WHSV and time on stream
were also examined and the results are discussed. 相似文献
10.
S. Vishnu Priya J. Herbert Mabel S. Gopalakrishnan M. Palanichamy V. Murugesan 《Journal of Porous Materials》2009,16(4):419-427
MAPO-36 was synthesized hydrothermally by isomorphic substitution of Mg2+ in the framework of AlPO-36 and ion-exchanged with Fe3+, Zn2+, La3+ and Ce3+ by wet method. The materials were characterized by XRD, TGA, TPD (ammonia) and SEM-EDX. XRD revealed absence of structural
degradation after ion-exchange. TPD (ammonia) showed selective ion-exchange of strong acid sites in ion-exchanged MAPO-36.
The weight loss around 550 °C in TGA for Fe, La and CeMAPO-36 suggested conversion of M(OH)2+ to MO+. Toluene disproportionation was carried over all catalysts in which diphenyl methane derivative was suggested to be the principle
intermediate in the formation of p-xylene and other products. The time on stream study showed exclusive formation of p-xylene after 6 h. 相似文献