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[en] The modelization of microwave propagation problems, including Eigen-value problem and scattering problem, is accomplished by the finite element method with vector functional and scalar functional. For Eigen-value problem, propagation modes in waveguides and resonant modes in cavities can be calculated in a arbitrarily-shaped structure with inhomogeneous material. Several microwave structures are resolved in order to verify the program. One drawback associated with the vector functional is the appearance of spurious or non-physical solutions. A penalty function method has been introduced to reduce spurious' solutions. The adaptive charge method is originally proposed in this thesis to resolve waveguide scattering problem. This method, similar to VSWR measuring technique, is more efficient to obtain the reflection coefficient than the matrix method. Two waveguide discontinuity structures are calculated by the two methods and their results are compared. The adaptive charge method is also applied to a microwave plasma excitor. It allows us to understand the role of different physical parameters of excitor in the coupling of microwave energy to plasma mode and the mode without plasma. (author)
[fr]Le sujet de cette these porte sur la modelisation de structures electromagnetiques (microonde) par la methode des elements finis. Deux types de probleme: celui aux valeurs propres (pour un systeme ferme) et celui de repartition (scattering), ont ete traites soit avec la fonctionnelle vectorielle soit avec la fonctionnelle scalaire. Pour le probleme aux valeurs propres, on peut resoudre les modes de propagation dans les guides d'onde et les modes de resonance dans les cavites de forme quelconque avec un milieu inhomogene. Pour tester la validite du programe plusieurs structures ont ete calculees. Des modes non-physiques peuvent apparaitre lorsqu'on resoud certaines structures par la fonctionnelle vectorielle (par exemple le guide d'onde charge de dielectrique); grace a la methode de 'penalite', on peut reduire le nombre de ces modes. Pour etudier la repartition des champs, une methode originale, appelee methode de la charge adaptee (simulation de la mesure du Taux d'Onde Stationnaire), a ete developpee; elle permet d'obtenir des resultats beaucoup plus rapidement qu'en utilisant la methode matricielle. Deux structures avec obstacles ont He calculees par les deux methodes et leurs resultats ont ete compares. La methode de la charge adaptee a ete egalement appliquee pour calculer des excitateurs de plasma. Cela a permis de mettre en evidence les conditions de transfert de l'energie sur le mode propre plasma par rapport a celui du mode sans plasma, ainsi que le role des divers parametres des excitateurs. (auteur)
[en] Under the condition of the pseudospin symmetry, the approximate analytical solution of the Dirac–Eckart problem with a Hulthén tensor interaction is investigated by working in a complete square integrable basis that supports a tridiagonal matrix representation of the wave operator. The pseudo-centrifugal term is treated with Greene and Aldrich's approximation scheme. The energy eigenvalue equation is obtained by diagonalization of the recursion relation and the corresponding spinor wave functions are presented in terms of Jacobi polynomials or hypergeometric functions.
[en] Based on the theory of wave propagation and scattering in random medium, the analysis method of the pulse propagating in the plasma medium is presented. Under the condition of strong fluctuations, we have deduced the two-frequency second moment and fourth moment equations, and calculated the two-frequency intensity correlation function and scintillation index in terms of the different electron density spectra. The statistical parameters of the self-correlation function, the correlation bandwidth and time are obtained, in order to provide a basis for studing the characteristic of the pulse propagation in plasma medium. (authors)
[en] This paper introduces weld metal properties of low alloy covered electrode E9018M (ASME B and V CODE, SEC.II, PART C, SFA 5.5) by means of mechanical tests. In accordance with the test results, main factors affect the weld metal properties consist of chemical contents, heat input, and status of the weld metal. It is possible to improve weld metal tensile strength and yield strength in a certain range by controlling heat input without changing classification of the covered electrode. (authors)
[en] We report the observation of ferromagnetism in topological insulator Co_0_._0_8Bi_1_._9_2Se_3 single crystal. The structural, magnetic, and microstructure properties of Co_0_._0_8Bi_1_._9_2Se_3 are investigated. The existence of complicated ferromagnetic ordering, indicates the anomalous second ferromagnetic phase transition below 30 K. Well-defined ferromagnetic hysteresis in the magnetization was found in the sample. The origin of bulk ferromagnetism in Co_0_._0_8Bi_1_._9_2Se_3 is concerned with three aspects: Co cluster, RKKY interactions, and the spin texture of Co impurities. - Highlights: • The bulk ferromagnetism have been found in the C_o_0_._0_8Bi_1_._9_2Se_3 single crystal. • The anomalous second ferromagnetic phase transition is found below 30 K. • The origin of bulk ferromagnetism in Co_0_._0_8Bi_1_._9_2Se_3 is concerned with three aspects.
[en] Objective: To investigate the changes of plasma levels of thromboxone A2 (TXA2) and prostacyclin (PGI2) and their relationship with pulmonary hypertension in patients with chronic obstructive pulmonary disease (COPD). Methods: The mean pulmonary arterial pressure (PaP) and plasma levels of thromboxone B2(TXB2) and 6-Keto-PGF1α (being the measurable stable metabolic product of TXA2 and PGI2 respectively) were measured in 30 COPD patients (with or without pulmonary hypertension) during remission and 37 controls. Besides, these variants were measured in 7 other COPD patients with acute exacerbation both at admission and after successful treatment. Results: During remission, the plasma TXB2 levels were significantly higher and plasma 6-Keto-PGF1α levels significantly lower with elevated TXB2/6-Keto-PGF1α ration in COPD patients with pulmonary hypertension than those in patients without pulmonary hypertension (P<0.01). Differences between these variants in COPD patients without pulmonary hypertension during remission and in the controls were not significant (P>0.05). PaP and TxB2 levels significantly decreased and 6-Keto-PGF1α increased with lower TXB2/6-Keto-PGF1α ratio after successful treatment in the 7 COPD patients with acute exacerbation (vs at admission, P<0.01). Analysis also revealed that PaP was positively correlative to TXB2 level and negatively correlated to 6-Keto-PGF1α level (r=+0.46 and -0.39 respectively, P<0.05). Conclusion: The imbalance between TXA2 and PGI2 plays an important role in the development of pulmonary hypertension in patients with COPD
[en] Reliability is an important issue affecting each stage of the life cycle ranging from birth to death of a product or a system. The reliability engineering includes the equipment failure data processing, quantitative assessment of system reliability and maintenance, etc. Reliability data refers to the variety of data that describe the reliability of system or component during its operation. These data may be in the form of numbers, graphics, symbols, texts and curves. Quantitative reliability assessment is the task of the reliability data analysis. It provides the information related to preventing, detect, and correct the defects of the reliability design. Reliability data analysis under proceed with the various stages of product life cycle and reliability activities. Reliability data of Systems Structures and Components (SSCs) in Nuclear Power Plants is the key factor of probabilistic safety assessment (PSA); reliability centered maintenance and life cycle management. The Weibull distribution is widely used in reliability engineering, failure analysis, industrial engineering to represent manufacturing and delivery times. It is commonly used to model time to fail, time to repair and material strength. In this paper, an improved Weibull distribution is introduced to analyze the reliability data of the SSCs in Nuclear Power Plants. An example is given in the paper to present the result of the new method. The Weibull distribution of mechanical equipment for reliability data fitting ability is very strong in nuclear power plant. It's a widely used mathematical model for reliability analysis. The current commonly used methods are two-parameter and three-parameter Weibull distribution. Through comparison and analysis, the three-parameter Weibull distribution fits the data better. It can reflect the reliability characteristics of the equipment and it is more realistic to the actual situation. (author)
[en] Highlights: • Al_1_1Cr_4 was prepared by diffusion of electrodeposited Al/Cr composite film. • The compositional range of Al_1_1Cr_4 was from Al75.0Cr25.0 to Al76.0Cr24.0. • The decomposition temperature of Al_1_1Cr_4 was 829 °C. - Abstract: Al–Cr alloys were prepared by making Al/Cr composite films go through a low temperature heat treatment. Al/Cr composite films were electrodeposited from aqueous solution and ionic liquid successively. The effects of the composition of Al/Cr composite film on the phase constitutions of Al–Cr alloy were then investigated. The samples were characterized by metallographic microscope (OM), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM) and spherical aberration corrected transmission electron microscope (Cs-TEM). The decomposition temperature of Al–Cr alloy was studied using differential thermal analysis. The results showed that single Al_1_1Cr_4 phase can be obtained from the Al/Cr composite film at the composition range of 75.0–76.0 at.% Al. The Al_1_1Cr_4 would decompose into Al_4Cr and Al_8Cr_5 at 829 °C
[en] If a district heating reactor is set up in north seashore cities of China and operated in such a way that it supplies heating for inhabitants in winter and produces fresh water from seawater in summer, the load factor of the reactor would be increased, and the problem of fresh water shortage would be solved, in addition, it would benefit environment and promote tourism
[en] Objective: To investigate the relationships between changes of serum sex hormones levels and protein-lipid metabolism in patients with ulcerative colitis. Methods: Serum levels of estradiol (E2) pregnenedione (P), prolactin(PRL), luteinizing hormone (LH), follicle-stimulating hormone (FSH) (with CLIA), sree testos (T, with RIA) and total-protein (TP), albumin (Alb), globulin (G), albumin/globulinratio (A/G) total-cholesterd (TC), high density lipoprotein cholesterols (LDL-C) (with biochemistry were determined in 72 patients) with ulcerative colitis and 72 controls. Results: The serum levels of T, LH, FSH, TP, Alb, A/G, TC, LDL-C in patients with ulcerative colitis were significantly lower than those in controls (P<0.01), while the serum levels of E2, PRL in patients with ulcerative colitis were significantly higher than those in controls (P<0.01). Correlation: analysis showed that the serum levels of E2 were negatively correlated with TP, A/G and TC (P<0.01), on the contrary,the serum levels of T were positively correlated with TP, TC (P<0.01). There were no linear correlation between LH, FSH and E2 levels in the female sex (P>0.05) as well as between LH, FSH and T levels in the male sex (P>0.05). Conclusion: The abnormal serum levels of sex hormone might contribute to the development of hypoproteinaemia and lowered lipid levels in patients with ulcerative colitis. Treatment with correction of serum sex hormones levels might be beneficial to the patients. (authors)