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31.
Exfoliation and related microstructures in 2024 aluminum body skins on aging aircraft 总被引:3,自引:0,他引:3
Maria Posada L. E. Murr C. -S. Niou D. Roberson D. Little Roy Arrowood Debra George 《Materials Characterization》1997,38(4-5):259-272
Exfoliation, a directional attack along elongated grain boundaries, has been examined in some detail in rolled 2024 aluminum sheet and plate for KC-135 aging aircraft body skin samples utilizing optical (light) metallography, scanning electron microscopy, and transmission electron microscopy. A detailed analysis and comparison of precipitates within the grains and in the grain boundaries were performed, as well as an examination of elemental depletion profiles across grain boundaries. These observations suggest that corrosion-related anodic sites play a far less significant role in the propagation of exfoliation than do the hard corrosion products creating wedging stresses within the elongated grain boundaries, which seem to demonstrate unique and unusual structural or energetic features or both. 相似文献
32.
Burke M 《Environmental science & technology》1996,30(10):436A
Government. 相似文献
33.
Anna Sztaniszlav Magdolna Balla Maria Farkas-Jahnke Csaba Novák 《Journal of Materials Science》1990,25(5):2353-2358
The kinetics of solid-state reactions of powdered reactants were investigated by X-ray and by differential thermogravimetry in a magnetic field. Measurements revealed mutual diffusion of the Fe3+ and In3+ ions in the Fe2O3-In2O3 system heat treated for 3 h at 700 to 1400° C. Diffusion of indium into the Fe2O3 lattice caused a shift of the Curie temperature of the antiferromagnetic iron oxide towards lower temperatures. Only Caln2O4 was found between CaCO3 and In2O3 up to 1400° C. Also, in the Fe2O3-CaCO3-In2O3in system, the reaction started with the mutual diffusion of iron and indium and the forming of CaFe2O4. End-products were the magnetic -Ca4Fe14O25 and CaFe4O7, and the non-magnetic CaFe5O7, depending on the In3+ concentration. Indium stabilized the magnetic calcium-iron oxide structures, shifting their Curie temperatures towards lower values. 相似文献
34.
Maria da Graça Marcos J.A. Tenreiro MachadoT.-P. Azevedo-Perdicoúlis 《Applied Soft Computing》2012,12(2):589-599
Kinematic redundancy occurs when a manipulator possesses more degrees of freedom than those required to execute a given task. Several kinematic techniques for redundant manipulators control the gripper through the pseudo-inverse of the Jacobian, but lead to a kind of chaotic inner motion with unpredictable arm configurations. Such algorithms are not easy to adapt to optimization schemes and, moreover, often there are multiple optimization objectives that can conflict between them. Unlike single optimization, where one attempts to find the best solution, in multi-objective optimization there is no single solution that is optimum with respect to all indices. Therefore, trajectory planning of redundant robots remains an important area of research and more efficient optimization algorithms are needed. This paper presents a new technique to solve the inverse kinematics of redundant manipulators, using a multi-objective genetic algorithm. This scheme combines the closed-loop pseudo-inverse method with a multi-objective genetic algorithm to control the joint positions. Simulations for manipulators with three or four rotational joints, considering the optimization of two objectives in a workspace without and with obstacles are developed. The results reveal that it is possible to choose several solutions from the Pareto optimal front according to the importance of each individual objective. 相似文献
35.
Maria Buuales Maria Cristina Ballesteros-Briones Manuela Gonzalez-Aparicio Sandra Hervas-Stubbs Eva Martisova Uxua Mancheo Ana Ricobaraza Sara Lumbreras Cristian Smerdou Ruben Hernandez-Alcoceba 《International journal of molecular sciences》2021,22(8)
Immune checkpoint inhibitors (ICIs) have demonstrated remarkable efficacy in a growing number of malignancies. However, overcoming primary or secondary resistances is difficult due to pharmacokinetics issues and side effects associated with high systemic exposure. Local or regional expression of monoclonal antibodies (mAbs) using gene therapy vectors can alleviate this problem. In this work, we describe a high-capacity adenoviral vector (HCA-EFZP-aPDL1) equipped with a mifepristone-inducible system for the controlled expression of an anti-programmed death ligand 1 (PD-L1) blocking antibody. The vector was tested in an immune-competent mouse model of colorectal cancer based on implantation of MC38 cells. A single local administration of HCA-EFZP-aPDL1 in subcutaneous lesions led to a significant reduction in tumor growth with minimal release of the antibody in the circulation. When the vector was tested in a more stringent setting (rapidly progressing peritoneal carcinomatosis), the antitumor effect was marginal even in combination with other immune-stimulatory agents such as polyinosinic-polycytidylic acid (pI:C), blocking mAbs for T cell immunoglobulin, mucin-domain containing-3 (TIM-3) or agonistic mAbs for 4-1BB (CD137). In contrast, macrophage depletion by clodronate liposomes enhanced the efficacy of HCA-EFZP-aPDL1. These results highlight the importance of addressing macrophage-associated immunoregulatory mechanisms to overcome resistance to ICIs in the context of colorectal cancer. 相似文献
36.
We prove the existence of a P-type (proportional-type) space-learning control, which, on the basis of a kinematic third order nonlinear model of an autonomous nonholonomic vehicle and by a proper choice of the proportional control gain, guarantees asymptotic tracking of planar curves whose uncertain curvature is L-periodic in the curvilinear abscissa. The behavior of a human driver, who repetitively learns the correct action from the past experience in the space, is mathematically reproduced. A stability analysis is presented while simulation results demonstrate the effectiveness of the presented approach. 相似文献
37.
Elisabetta Tornatore Pasquale Vetro Stefania Maria Buccellato 《Neural computing & applications》2014,24(2):309-315
We propose a stochastic disease model where vaccination is included and such that the immunity is permanent. The existence, uniqueness, and positivity of the solution and the stability of the disease-free equilibrium are studied. 相似文献
38.
Two samples of poly(diethoxyphosphazene) (PDEP) having very different molecular weights have been studied by viscometry and size exclusion chromatography in THF solution. The results obtained, together with light scattering data of these samples, allow the calculation of the Mark-Houwink constants a=0.65 and K=2.5 10-4 in THF at 25°C. The method of calculation employed takes into account the great polydispersity of the samples. The characteristic ratio of the unperturbed dimensions was also calculated giving Cn = r2o/n2 18, a value slightly higher than those previously reported for poly(dihexoxyphosphazene), Cn13 and poly (dichlorophosphazene), Cn13.5. 相似文献
39.
Luis A. Garcia Maria Antonieta Alfaro Ricardo Bressani 《Journal of the American Oil Chemists' Society》1987,64(3):371-375
Oils from a selection ofAmaranthus caudatus, A. hypochondriacus andA. cruentus were extracted with hexane. The crude oils were analyzed for acid value, saponification and iodine number, and were included
in basal casein diets for rat studies at 5 and 10% levels to replace equal amounts of refined cottonseed oil. The oils fromA. cruentus andA. hypochondriacus were similar in the oil properties studied and different fromA. caudatus. At either 5 or 10% food intake levels, weight gain and PER were not statistically different from values reported for cottonseed
oil. True digestibility of amaranth oil was lower than that of cottonseed oil.A. cruentus oil gave the lowest digestibility. Oil levels induced statistical differences in food intake and digestibility. Oils fromA. caudatus, A. hypochondriacus and cottonseed induced similar serum cholesterol levels, while oil fromA. cruentus gave statistically higher values. Hemoglobin, hematocrit and serum proteins were similar among all groups. Microscopic analysis
of the organs of the rats revealed some changes that were also found in cottonseed oil-fed rats. It was concluded that crude
amaranth oil has lower digestibility than cottonseed oil, but that it is not responsible for growth-depressing effects when
the seed is fed raw as compared to processed materials. 相似文献
40.
Worldwide, cervical cancer is the second most common cancer in women, after breast cancer. The prevalence of this malignant disease is estimated at 1.4 million cases worldwide, causing about 290,000 deaths and 500,000 new cases per year, of which 80% correspond to women living in developing countries. In this work we propose a family of ordered models for basal cells of the cervix corresponding to different stages ranging from normal cells to the formation of precancerous lesions. We analyse the first member of the family analytically and for the second member we developed a non-standard numerical method in order to extract some biological information. 相似文献