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81.
The system KPO3-LaP3O9 has been studied for the first time by differential thermal analysis and X ray diffraction. The system shows two compounds KLa(PO3)4 and K2La(PO3)5 which melt in a peritectic decomposition at 880°C and 770°C respectively. An eutectic point appears at 705°C; The eutectic point corresponds to a concentration of 10% molar LaP3O9.Infra Red absorption spectra are typical of chain phosphates.The new compound K2La(PO35 is isotypic whith (NH4)2La(PO3)5 which has been synthetized for the first time. They belong to the triclinic system whith space group P1 and Z = 2. The parameters of the unit cell are: α = 90°3(1) β = 109°17(7) γ = 89°90(4) for K2La(PO3)5 and: α = 90°6(2) β = 107°4(1) γ = 89°82(7) for (NH4)2La(PO3)5. 相似文献
82.
83.
A single-parameter geometry to describe soil is achieved for Monte Carlo calculation of absorbed dose rate in air for photon emitters from natural radionuclides. This optimised geometry based on physical assumptions consists of the soil part whose emitted radiation has a given minimum probability to reach the detector. This geometry was implemented in Geant4 toolkit and a significant reduction in computation time was achieved. Simulation tests have shown that for soil represented by a cylinder of 40 m radius and 1 m deep, >98% of the calculated dose rate conversion coefficients in air at 1 m above the ground is generated by only 6% of the soil volume in the case of uniform distribution of radioactivity, and >99.2% of the calculated dose rate for an exponential distribution. When the soil is represented by the entire optimised geometry, 99% of the conversion coefficients values are reached for a soil depth of 1 m and 100% for that of approximately 2 m. 相似文献
84.
Glaoui Mohamed Trabelsi Hichem Zairi Hsan Gharsallah Ali Baudrand Henri 《International Journal of Electronics》2013,100(5):537-548
This article presents a new hybrid technique which combines two different numerical methods in the frequency domain, namely the Frequency Domain Transmission Line Matrix ( fdtLM) and the Wave Concept Iterative Process, to analyse three-dimensional (3D) microwave structures. As a result, a considerable reduction of the computation time and required computer memory is achieved compared with the classic fdtLM. The good agreement between simulation results and experimental published data validates the present analysis approach. 相似文献
85.
Contribution to analytical and numerical study of combined heat and moisture transfers in porous building materials 总被引:2,自引:0,他引:2
In this paper, one-dimensional model for evaluating coupled heat and moisture transfer in porous building materials was proposed. The transient partial differential equations system was solved analytically for Dirichlet boundary conditions. It consists first to introduce the Laplace transformation and then to use the potential function technique. This approach allows simplifying the initial mathematical problem to a fourth order ordinary differential equation which can be easily solved. This solution was used to assess the transient temperature and moisture distribution across materials. A comparison with numerical models from Luikov [2] and Vafai et al. [12] was performed, a good agreement was obtained. 相似文献
86.
87.
Hajer Trabelsi Faouzi Sakouhi Justin Renaud Pierre Villeneuve Mohamed L. Khouja Paul Mayer Sadok Boukhchina 《European Journal of Lipid Science and Technology》2012,114(8):968-973
A comparative study was performed to determine the fatty acid, 4‐desmethylsterol and triterpenic alcohols compositions of three different Tunisian populations of Pistacia lentiscus fruit Rimel (RM), Korbous (KO), and Tebaba (TB). Fruits are rich in lipids, which varied from 39.37% (KO) to 42.48% (TB) on a dry weight basis. Qualitatively, fatty acid, sterol, mono‐ and dimethylsterol composition is identical for all populations. Oleic acid was the major fatty acid for all samples, accounting from 40.49% in TB population to 50.72% in RM population followed by the palmitic and linoleic acids. Other fatty acids are present at lower levels. Total sterol amount varied from 109.72 mg/100 g of oil (KO) to 434.26 mg/100 g of oil (RM) with an average of 248.74 mg/100 g of oil. The major 4‐desmethylsterol component in all studied Tunisian populations of P. lentiscus oil was ß‐sitosterol followed by campesterol in TB and KO, and by stigmasterol in RM. The amount of total triterpenic alcohols varied from 42.39 mg/100 g of oil in RM population to 70.41 mg/100 g oil in TB population. The quantitative difference in the fatty acids and 4‐desmethylsterols of the different populations studied could be due to the effect of geographic region and soil type. 相似文献
88.
Olfa Baâtour Hela Mahmoudi Imen Tarchoun Nawel Nasri Najla Trabelsi Rym Kaddour Maha Zaghdoudi Ghaith Hamdawi Riadh. Ksouri Mokhtar Lachaâl Brahim Marzouk 《Journal of the science of food and agriculture》2013,93(1):134-141
BACKGROUND: Two varieties of Origanum majorana (Canadian and Tunisian) were evaluated for their phenolic, flavonoid and tannin contents, individual phenolic compounds and antioxidant activities under NaCl constraint. RESULTS: The results showed a significant variability in phenolic composition and antioxidant behavior between the two varieties under salt stress. The phenolic composition of methanolic extracts was determined by reversed‐phase high‐performance liquid chromatography. Amentoflavone was the predominant flavonoid compound; in addition, trans‐2‐hydrocinnamic acid became the major phenolic acid with salt treatment of the Tunisian variety. In the control, Canadian variety extract was characterized by high levels of gallic acid and amentoflavone. However, under 75 mmol L?1 NaCl, gallic acid content doubled, whereas amentoflavone content was maintained in the Canadian variety. Stimulation of phenolic acid biosynthesis was observed in these two varieties under salt treatment despite the fact that shoots of the Tunisian variety showed higher antioxidant activities compared to those from the Canadian variety. Tunisian O. majorana might have developed tolerance to salinity and avoided tissue damage by activating enzymes involved in the galactosylation of quercetin into quercetin‐3‐galactoside and quercetin‐3‐rhamnoside. CONCLUSION: Our results confirmed the tolerance of Tunisian O. majorana plants. Copyright © 2012 Society of Chemical Industry 相似文献
89.
90.
Effects of Stitching on Delamination of Satin Weave Carbon-Epoxy Laminates Under Mode I,Mode II and Mixed-Mode I/II Loadings 总被引:1,自引:0,他引:1
The objective of the present study is to characterize the effect of modified chain stitching on the delamination growth under
mixed-mode I/II loading conditions. Delamination toughness under mode I is experimentally determined, for unstitched and stitched
laminates, by using untabbed and tabbed double cantilever beam (TDCB) tests. The effect of the reinforcing tabs on mode I
toughness is investigated. Stitching improves the energy release rate (ERR) up to 4 times in mode I. Mode II delamination
toughness is evaluated in end-notched flexure (ENF) tests. Different geometries of stitched specimens are tested. Crack propagation
occurs without any failure of stitching yarns. The final crack length attains the mid-span or it stops before and the specimen
breaks in bending. The ERR is initially low and gradually increases with crack length to very high values. The mixed-mode
delamination behaviour is investigated using a mixed-mode bending (MMB) test. For unstitched specimens, a simple mixed-mode
criterion is identified. For stitched specimens, stitching yarns do not break during 25% of mode I ratio tests and the ERR
increase is relatively small compared to unstitched values. For 70% and 50% of mode I ratios, failures of yarns are observed
during crack propagation and tests are able to capture correctly the effect of the stitching: it clearly improves the ERR
for these two mixed modes, as much as threefold. 相似文献