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排序方式: 共有129条查询结果,搜索用时 156 毫秒
21.
Alpay Şahin Erdem Alp Demet Eserci H. Canan Cabbar 《Chemical Engineering Communications》2017,204(10):1129-1142
In this study, Al2O3, ZrO2, and Al2O3–ZrO2 composite materials were prepared with the sol–gel technique. X-ray diffraction analysis, differential scanning calorimetry–thermogravimetry, scanning electron microscopy–energy-dispersive X-ray spectrometry, nitrogen adsorption isotherm measurements, and helium pycnometry were used to characterize the resultant materials. Effective diffusion coefficients of helium and hydrogen and the adsorption equilibrium constant of hydrogen in the resultant materials were determined using single-pellet moment technique. The effective diffusivities of helium and hydrogen in both ZrO2 and Al2O3–ZrO2 composite pellets were found to be smaller than the value found for Al2O3, due to the lower tortuosity factor values of the Al2O3 pellet. It was found that hydrogen was weakly adsorbed on all resultant materials. 相似文献
22.
Demet Apaydin Ahmet Sukru Demirci Umit Gecgel 《Journal of the American Oil Chemists' Society》2017,94(1):57-67
In the present study, grape seed samples (Alicante Bouschet, Cabernet Franc, Cinsault, Merlot, Shiraz) were treated with 1.0, 3.0, 5.0, and 7.0 kGy of gamma radiation. Effect of irradiation dose on free fatty acids (FFA), peroxide value (PV), sterol, fatty acid composition, phenolic content, antioxidant activity of the seed oils, and chemical (dry matter, fat, ash, total sugar, invert sugar) changes of grape seeds were determined. Regarding fatty acid composition, oleic acid (C18:1) and linoleic acid (C18:2) levels decreased. β-sitosterol content with a highest percentage among sterols in grape seed oils decreased due to gamma irradiation. Generally gamma irradiation increased free fatty acids and peroxide value of the oils; however, phenolic content and antioxidant capacity of grape seeds decreased. 相似文献
23.
This paper presents a laboratory study on the performance of concrete by adding mineral admixtures, silica fumes (SF) or/and fly ash (FA). Performance of the concrete mixes was determined with short and long-term tests, which include compressive strength, porosity, capillary absorption, wet–dry cycle and accelerated carbonation. The test results, in general, showed that mineral admixtures improved the performance of concretes. SF contributed to both short and long-term properties of concrete, whereas FA shows its beneficial effect in a relatively longer time. As far as the compressive strength is concerned, adding of both SF and FA slightly increased compressive strength, but contributed more to the improvement of transport properties of concretes. 相似文献
24.
Kravchik T Oved S Paztal-Levy O Pelled O Gonen R German U Tshuva A 《Radiation protection dosimetry》2008,131(4):418-424
Inhalation is the main route of internal exposure to radioactive aerosols in the nuclear industry. To assess the radiation dose from the intake of these aerosols, it is necessary to know their physical (aerodynamic diameter distribution) and chemical (dissolution rate in extracellular lung fluid) characteristics. Air samples were taken from the uranium processing plant at the Nuclear Research Center, Negev. Measurements of aerodynamic diameter distribution using a cascade impactor indicated an average activity median aerodynamic diameter value close to 5 microm, in accordance with the recent recommended values of International Commission on Radiological Protection (ICRP) model. Solubility profiles of these aerosols were determined by performing in vitro solubility tests over 100 d in a simultant solution of the extracellular fluid. The tests indicated that the uranium aerosols should be assigned to an absorption between Types M and S (as defined by the ICRP Publication 66 model). 相似文献
25.
Gonen R Marco R German U Katorza E Alfassi ZB Haquin G Tshuva A Pelled O 《Radiation protection dosimetry》2007,125(1-4):460-464
The Organic Bound Tritium (OBT) amount in the body may induce changes in the evaluation of the internal exposure to tritium, due to its different retention time relative to HTO. OBT measurements for urine are not performed routinely, mainly because of the lengthy work needed in preparation of the samples, when using the standard oxygen combustion method. A simpler and more rapid method based on liquid scintillation counting (LSC) was employed, and an evaluation was performed to check its suitability for urine samples. The principle of the proposed method is based on subtracting the LSC counts of the water phase sample (HTO) from the total activity of the urine sample (OBT+HTO). A good correlation was found between the results obtained when applying the proposed direct method and the Gold standard method. The minimum detectable activity when using this method was determined. 相似文献
26.
Economically usable water resources per capita are decreasing due to excessive population increase each year in Turkey. For this reason, new water resources should be found in the near future. The potential water resources are seawater or well water both of which need removal of salinity. The most promising treatment method for salinity is reverse osmosis. While reverse osmosis becomes widespread, the cost of the process will decrease. There is no detailed information about cost of seawater desalination in Turkey. In this study, a cost analysis of seawater desalination in Turkey was performed for reverse osmosis systems. The basic parameters of cost analysis such as capacity, recovery, membrane life, energy, chemical costs and flux were evaluated based on the effects on capital, operating and total production costs. 相似文献
27.
Shelf life of cultured sea bass packaged in air, vacuum, and gas mixture packages stored for 40 days at 2.90±0.02°C was compared. The gas mixtures used contained CO2, O2, and N2 at difference percentages (M1: 75% CO2/25% N2; M2: 60% CO2/40% N2; M3: 30% O2/30% CO2/40% N2). Sensory and physical parameters, chemical changes, and microbiological counts were monitored during storage. Storage with a gas mix including 75 and 60% CO2 was more effective than vacuum processing and packaging with a gas mix that included oxygen. Vacuum was the most effective method for preventing lipid oxidation. The optimum method for sea bass in view of all analysis results was modified atmosphere packaging (MAP) and the most suitable gas mix ratio was 75% CO2/25% N2. The best days for consumption of sea bass packaged with air, MAP (M1, M2, and M3), and vacuum were 4th, 28th, 28th, 16th, and 20th days, respectively. 相似文献
28.
Demet Aydınoğlu Özkan Akgül Vildan Bayram 《Polymer-Plastics Technology and Engineering》2013,52(16):1706-1722
Polacrylamide nanocomposite hydrogels were prepared by in situ free radical polymerization reaction in presence of Spirulina microalgae, which is immobilized in montmorillonite clay (Sp-MMT). The nanocomposite hydrogel having 1 wt.% Sp-MMT clay was found to have desired exfoliated structure, maximum swelling and improved thermal stability. It also showed maximum metal adsorption capacity, which is about 312% higher than that of neat PAAm hydrogel at the highest metal concentration. The presence of Spirulina's porous network structure where all potential binding sites are under receptive position was found to be responsible for the dramatic increase in the metal adsorption and swelling behavior. 相似文献
29.
The adsorption of Th4+ ions was studied on composites of polyacrylamide (PAAm) with montmorillonite (Mt), clinoptilolite (Z) and zeolite Y (ZY), and after phytic acid (Phy) modification.The monolayer adsorption capacity was 0.33 and 0.65 mol kg? 1 for PAAm-Mt and PAAm-Mt-Phy, 0.07, 0.21 and 0.60 mol kg? 1 for Z, PAAm-Z and PAAm-Z-Phy, and 0.74, 0.89 and 1.18 mol kg? 1 for ZY, PAAm-ZY and PAAm-ZY-Phy. The enthalpy and entropy changes were positive for all adsorbents. The adsorption kinetics followed the pseudo-second order model indicating that the rate controlling step was chemical adsorption by ion exchange. The reusability tests for five uses proved that the PAAm-Mt and PAAm-Z were reusable and complete recovery of the adsorbed ions was possible. ZY and the composites modified with Phy were not reusable. The presence of foreign metal cations did not influence the Th4+ adsorption. The adsorbed Th4+ onto the columns was effectively recovered with diluted HNO3. 相似文献
30.