Design for active and passive flutter suppression and gust alleviation

Analytical design techniques for active and passive control of aeroelastic systems are based on a rational approximation of the unsteady aerodynamic loads in the entire Laplace domain, which yields matrix equations of motion with constant coefficients. Some existing schemes are reviewed, the matrix Pade approximant is modified, and a technique which yields a minimal number of augmented states for a desired accuracy is presented. The state-space aeroelastic model is used to design an active control system for simultaneous flutter suppression and gust alleviation. The design target is for a continuous controller which transfers some measurements taken on the vehicle to a control command applied to a control surface. Structural modifications are formulated in a way which enables the treatment of passive flutter suppression system with the same procedures by which active control systems are designed

Sous-produits de réaction formés lors de la filtration sur charbon actif de composés phénoliques en présence d'ions chlorite

L'étude des interactions entre les ions chlorite, un charbon actif en grains (CAG CECA 40) et des composés phénoliques (phénol et para-nitrophénol) a été réalisée à partir d'expériences de filtration sur mini-colonnes de CAG de solutions aqueuses de chlorite et du composé organique en mélange ([C102-] inf=50 mg.l-¹; [Composé Organique]jnf=200 µmol.l-¹ ; 3 g de CAG; Vitesse de filtration: 3,7 m.h-¹). Les résultats obtenus ont permis de montrer que la présence de chlorite conduit à une augmentation des capacités du CAG vis-à-vis de l'élimination du phénol et du para-nitrophénol. Cette augmentation résulte de réactions chimiques entre le composé organique et les sous-produits de décomposition des ions chlorite par le charbon actif. Les analyses par couplage CG/SM des extraits issus des charbons actifs à la fin des filtrations ont permis de mettre en évidence la présence de nombreux composés adsorbés sur le charbon actif. Les composés identifiés résultent de réactions d'oxydation, de deshydroxylation, de carboxylation, d'halogénation, d'hydroxylation et de dimérisation. L'action des ions chlorite sur le charbon actif peut conduire à la formation de radicaux à la surface du charbon actif ou en solution capables de réagir avec les composés organiques pour former les sous-produits observés.The use of chlorine dioxide for the chemical preoxidation of potable water with high oxidant demand requires that the major inorganic byproduct, chlorite, in the treatment system be removed, owing to the potential toxicity of this oxychlorine species. Granular Activated Carbon (GAC) filtration, in converting chlorite ions into chloride, appears to be an interesting approach, but very few data are available concerning possible interactions in the presence of organic matter. The present research was designed to examine the influence of phenolic compounds on the efficiency of activated carbon in removing chlorite and to study the reactions between chlorite, activated carbon and organic molecules. Laboratory experiments have been carried out with relatively high substrate concentrations in order to identify the resulting byproducts.Materials and Methods.Filtrations of solutions containing chlorite and a phenolic compound (phenol or para nitrophenol; [Organic Compound]inf=200 µmol.L-¹;[C102-] inf=50 mg L-¹; pH=7.2); were performed using 1- cm i.d. glass columns packed with 3.0 g of GAC CECA 40 (Flow rate: 3.7 m.h-¹). Inorganic species were analysed by HPLC, with an anion column and a conductimetric detector for chloride and chlorate, and with a C-18 column and a UV detector for chlorite. Phenol and para nitrophenol were also analysed by HPLC, in the reverse mode. At the conclusion of the filtrations, the Total Organic Halogen (TOX) adsorbed on the carbon was determined after combustion of the carbon and measurement of the liberated halides with a micro coulometer (Dohrmann DX20). In order to identify organic reaction byproducts, carbon samples were Soxhlet extracted with methylene chloride and half of the extracts were methylated with diazomethane. Identification of the organic products was then carried out by gas chromatography / mass spectrometry with a DB5 capillary column and a quadrupolar hyperbolic filter system CPV/MS.Results and Discussion.Effects of phenol and p nitrophenol on removal of chlorite by GAC. The effluent curves from columns that received solutions containing both chlorite and an organic solute (columns A and B; fig. 1) showed that the presence of phenol or p nitrophenol in the influent decreases the capacity of GAC to remove chlorite.Effect of chlorite on removal of phenol and p nitrophenol. An increase in the cumulative removal of the organic solute was observed for columns A and B compared with columns that received solutions of the phenolic compound only (fig. 2; table 11). p benzoquinone was found in the eff1uent of column A fed with a chlorite phenol solution (fig. 3).Formation of organic byproducts by reactions between chlorite and phenol or p nitrophenol in the presence of GAC. TOX analyses showed that interactions between chlorite, GAC, and phenol or p nitrophenol led to the production of organohalogenated compounds. These data clearly demonstrate that halogenation reactions take place in the GAC bed and that a fraction of the total amount of phenol or p nitrophenol removed can be due to chemical reactions. GC/MS analyses of GAC extracts of columns A and B (tables IV and V) indicated that the phenol chlorite GAC reactions yield a variety of organic byproducts that are produced by hydroxylation and carboxylation of the aromatic ring by oxidation to quinones, by chlorine substitution and by dehydroxylation and dimerization reactions. Fewer products could be identified in the reaction between p nitrophenol, chlorite, and GAC. Since chlorite is unreactive with phenol and p nitrophenol in neutral aqueous solution, the formation of these organic byproducts can be attributed to reactions between phenol or p nitrophenol present in the GAC pore solution or adsorbed on GAC and the chemical species (Cl· ClO·, ClO2, HOCl (ClO-), surface free radicals ...) generated from the reaction of chlorite and carbon. Thus, aromatic acids could come from radical processes between adsorbed molecules and carbon surface functional groups oxidized by chlorite. The formation of dimers can also be explained by a freeradical mechanism. The reactions between Cl·, ClO· radicals or radicals present on the GAC surface, with organic compounds produce organic radicals via H atom abstraction or one electron transfer. Organic radicals such as phenoxy radicals or other aromatic radicals can then undergo dimerization by carbon-oxygen or carbon-carbon coupling. The formation of organochlorinated compounds can be explained by the reaction of chlorine (HOCl, ClO-) and chlorine radicals with organic molecules present in the solution. However further investigation is needed in order to evaluate if such compounds can be formed on GAC filters and then desorbed in the effluent in thc case of drinking waters pretreated with chlorine dioxide

Consistent Anisotropic Repulsions for Simple Molecules

We extract atom-atom potentials from the effective spherical potentials that suc cessfully model Hugoniot experiments on molecular fluids, e.g., $O_2$ and $N_2$. In the case of $O_2$ the resulting potentials compare very well with the atom-atom potentials used in studies of solid-state propertie s, while for $N_2$ they are considerably softer at short distances. Ground state (T=0K) and room temperatu re calculations performed with the new $N-N$ potential resolve the previous discrepancy between experimental and theoretical results.Comment: RevTeX, 5 figure

Robust Design for Aeroelastically Tailored/Active Aeroelastic Wing

Presented at the 7th AIAA/USAF/NASA/ISSMO Symposium on Multidisciplinary Analysis and Optimization, St. Louis, MO, September 2-4, 1998.A study of multidisciplinary design concerning the incorporation of aeroelastic tailoring, control surface blending, and active aeroelastic wing concepts is presented. The design process incorporates response surfaces, fast probability integration and modal-basis multidisciplinary design optimization to characterize the design space. The wing box skins of a representative fighter configuration with multiple wing control surfaces are sized to minimum weight. A design of experiments approach is developed for the gear ratios in control surface blending. Design optimization is conducted for each set of gearing functions. The control surface gear ratios are then treated as noise in the structural design process, and a robust structural design is sought to account for the change in control laws that historically occur during the aircraft design process. The motivation for this methodology investigation is derived from the common occurrence of control law changes throughout the lifetime of an aircraft

BICEP3: a 95 GHz refracting telescope for degree-scale CMB polarization

BICEP3 is a 550 mm-aperture refracting telescope for polarimetry of radiation in the cosmic microwave background at 95 GHz. It adopts the methodology of BICEP1, BICEP2 and the Keck Array experiments - it possesses sufficient resolution to search for signatures of the inflation-induced cosmic gravitational-wave background while utilizing a compact design for ease of construction and to facilitate the characterization and mitigation of systematics. However, BICEP3 represents a significant breakthrough in per-receiver sensitivity, with a focal plane area 5$\times$ larger than a BICEP2/Keck Array receiver and faster optics ($f/1.6$ vs. $f/2.4$). Large-aperture infrared-reflective metal-mesh filters and infrared-absorptive cold alumina filters and lenses were developed and implemented for its optics. The camera consists of 1280 dual-polarization pixels; each is a pair of orthogonal antenna arrays coupled to transition-edge sensor bolometers and read out by multiplexed SQUIDs. Upon deployment at the South Pole during the 2014-15 season, BICEP3 will have survey speed comparable to Keck Array 150 GHz (2013), and will significantly enhance spectral separation of primordial B-mode power from that of possible galactic dust contamination in the BICEP2 observation patch.Comment: 12 pages, 5 figures. Presented at SPIE Astronomical Telescopes and Instrumentation 2014: Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VII. To be published in Proceedings of SPIE Volume 915

BICEP2 / Keck Array VIII: Measurement of gravitational lensing from large-scale B-mode polarization

We present measurements of polarization lensing using the 150 GHz maps which include all data taken by the BICEP2 & Keck Array CMB polarization experiments up to and including the 2014 observing season (BK14). Despite their modest angular resolution ($\sim 0.5^\circ$), the excellent sensitivity ($\sim 3\mu$K-arcmin) of these maps makes it possible to directly reconstruct the lensing potential using only information at larger angular scales ($\ell\leq 700$). From the auto-spectrum of the reconstructed potential we measure an amplitude of the spectrum to be $A^{\phi\phi}_{\rm L}=1.15\pm 0.36$ (Planck $\Lambda$CDM prediction corresponds to $A^{\phi\phi}_{\rm L}=1$), and reject the no-lensing hypothesis at 5.8$\sigma$, which is the highest significance achieved to date using an EB lensing estimator. Taking the cross-spectrum of the reconstructed potential with the Planck 2015 lensing map yields $A^{\phi\phi}_{\rm L}=1.13\pm 0.20$. These direct measurements of $A^{\phi\phi}_{\rm L}$ are consistent with the $\Lambda$CDM cosmology, and with that derived from the previously reported BK14 B-mode auto-spectrum ($A^{\rm BB}_{\rm L}=1.20\pm 0.17$). We perform a series of null tests and consistency checks to show that these results are robust against systematics and are insensitive to analysis choices. These results unambiguously demonstrate that the B-modes previously reported by BICEP / Keck at intermediate angular scales ($150\lesssim\ell\lesssim 350$) are dominated by gravitational lensing. The good agreement between the lensing amplitudes obtained from the lensing reconstruction and B-mode spectrum starts to place constraints on any alternative cosmological sources of B-modes at these angular scales.Comment: 12 pages, 8 figure