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1.
2.
Earth-orbiting spacecraft often contain solar arrays or antennas supported by a preloaded mast. Due to weight and cost considerations, the supporting structures of the spacecraft appendages are made extremely light and flexible. Therefore, it is essential to investigate the influence of all physical and structural parameters on the dynamic behavior of the overall structure. The governing equation of motion and its general solution for the preloaded mast are developed. Furthermore, the mass moment of inertia of the mast subjected to bending vibrations is included in the governing equation of motion to investigate its influence on determining the circular frequencies. To verify the developed formulations, a finite element technique was implemented. The accuracy and limitation of the technique on calculating the circular frequencies are discussed. Although the study described in this paper primarily focuses on the mast for the space station solar arrays, the developed formulations and techniques can be applied to any large and flexible beam in zero gravity. 相似文献
3.
We consider a discrete-time stochastic model of an ECN/RED gateway where competing TCP sources share the link capacity. As
the number of competing flows becomes large, the asymptotic queue behavior (normalized by the number of flows) at the gateway
can be described by a simple recursion and the throughput behavior of individual TCP flows becomes asymptotically independent.
A Central Limit Theorem complement is also presented, yielding a more accurate characterization of the asymptotic queue size.
These results suggest a scalable yet accurate model of this complex large-scale stochastic feedback system, and crisply reveal
the sources of queue fluctuations.
This work was prepared through collaborative participation in the Communications and Networks Consortium sponsored by the
U.S. Army Research Laboratory under the Collaborative Technology Alliance Program, Cooperative Agreement DAAD19-01-2-0011.
This work was also supported by the Space and Naval Warfare Systems Center—San Diego under Contract No: N66001-00-C-8063.
The views and conclusions contained in this document are those of the authors and should not be interpreted as representing
the official policies, either expressed or implied, of the Army Research Laboratory or the U.S. Government. 相似文献
4.
The mass spectra of the three cyclopentane-1,2,3-triols, six cyclopentane-tetrols and four cyclopentane-pentols stereoisomers have been studied. Complex processes, especially regarding the H2O eliminations, were detected by extensive deuterium labelling. 相似文献
5.
Oliver Moers Violeta Latorre Karl‐Heinz Nagel Armand Blaschette Peter G. Jones 《无机化学与普通化学杂志》2003,629(1):83-90
Polysulfonylamines. CLX. Crystal Structures of Metal Di(methanesulfonyl)amides. 10. The Three‐Dimensional Coordination Polymers M[(CH3SO2)2N], where M is Potassium, Rubidium, Cesium (Isotypic Structures for M = K, Rb) Low‐temperature X‐ray crystal structures are reported for KA (monoclinic, space group P21/c, Z′ = 1), RbA (isotypic and isostructural with KA), and CsA (monoclinic, P21/n, Z′ = 1), where A— denotes the anion obtained by deprotonation of the strong nitrogen acid (MeSO2)2NH. In KA and RbA, the anion is distorted into a rare C1 conformation, whereas the standard C2 conformation is retained in the cesium complex. The structures consist of three‐dimensional coordination networks, in which each cation adopts an irregular (O6N)‐heptacoordination by forming close contacts to one (O, N)‐chelating, one (O, O)‐chelating and three κ1O‐bonding ligands; however, the coordination number for Cs+ is effectively increased to 8 by a very short Cs···Cs contact distance of 422.5 pm. The crystal packings of the isotypic compounds KA and RbA display lamellar layer substructures that involve six independent ligand‐metal bonds and comprise an internal cation lamella and peripheral regions built up from anion monolayers; the 3D framework is completed by one independent M—O bond cross‐linking the layer substructures. In contrast, CsA features anion monolayers that intercalate planar zigzag chains of cations (Cs···Cs alternatingly 422.5 and 487.5 pm, Cs···Cs···Cs 135.7°), whereby each chain is surrounded and coordinated by four anion stacks and each anion stack connects two cation chains. All structures exhibit close C—H···A interanion contacts consistent with weak hydrogen bonding. 相似文献
6.
Pierre-Alain Blane Fazil O. Gülaar Armand Buchst 《Journal of mass spectrometry : JMS》1980,15(4):198-201
The mechanisms of formation of the ionized acid and the protonated acid fragments in the electron impact induced fragmentation of the title compounds were investigated. The well known mechanisms of hydrogen transfer through mono- and bicyclic transition states that occur in the molecular ions of carboxylic esters are not the main pathways giving rise to these fragments. The major component of the m/z 172 peak corresponding formally to ionized p-toluenesulfonic acid in fact has a different structure; its formation involves a complex mechanism including a double hydrogen transfer reaction. 相似文献
7.
A Comparison of the chemical ionisation and elctron-impact mass spectra of alkyl and aryl aminoketones has bee carried out. This has revealed the particular stabilization of the N-aryl grops in all cases. 相似文献
8.
Joseph Armand Yvette Armand Line Boulares Christian Bellec Jean Pinson 《Journal of heterocyclic chemistry》1985,22(6):1519-1525
The reaction of o-phenylenediamine with a β-ketoacid, leads in most cases to quinoxalinones. Their structure has been determined as well as that of their corresponding hydrazones. The reaction of hydrazine with these quinoxalinones gives dihydropyridazino[3,4-b]quinoxalines, the structure of which has been ascertained. It has been shown that among the six possible formulas, the only 1,2-dihydro structure fits with the spectroscopic data. On the contrary, N-substituted o-phenylenediamines lead to 2,10-dihydro derivatives. The electrochemical behavior of the 2,10-dihydro-10-methyl-3-phenylpyridazino[3,4-b]quinoxaline has been investigated. It has also been shown that the 3,4,6-trichloropyridazine reacts with o-phenylenediamines to give 5,10-dihydropyridazino[3,4-b]quinoxalines. These compounds can be oxidized to give the new heterocycle pyridazino[3,4-b]quinoxaline. 相似文献
9.
Fazil O. Gülaar Franois Mermound F. Johann Winkler Armand Vuchs 《Helvetica chimica acta》1984,67(2):488-501
Ammonia chemical ionization (CI) mass spectra of various open-chain, cyclic and unsaturated C5- to C10-alcohols were obtained at source temperatures ranging from 60° to 250°C. The reactivity of the ammonia adduct ion MNH and its fragmentation channels are characteristic for substrate structure. Although strongly temperature-dependent, the spectra give nevertheless information on the OH-group environment as well as on the C-skeleton at any source temperature. Primary, secondary and tertiary alcohols as well as allylic and simple olefinic alcohols can be distinguished by their spectra, which show ammonium adduct ions [MNH4]+, adduct dehydrogenation ions [MNH4-H2], ammonium substitution ions [MNH4-H2O]+ and [M-OH]+-ions as the main characteristic peaks. Moreover, konfigurational assignments of stereoisomeric alcohols are possible for larger substrate-size and source-temperature ranges than with isobutane CI mass spectrometry. Homologous M NH-ions show molecular-size control of fragmentation and linear MNH-ions are less stable than branched isomers due to incomplete energy randomization. 相似文献
10.
Alain Glangetas Fazil O. Gülacar Jean M. J. Tronchet Armand Buchs 《Helvetica chimica acta》1980,63(6):1740-1747
Electron Impact Mass Spectrometry of the 3-Desoxy-1,2: 5,6-di-O-isopropylidene-3-methylidene-δ-D -hexofuranose and Some C(3′)-Substituted Analogues The mass spectra of the 3-desoxy-1,2:5, 6-di-O-isopropylidene-3-methylidene- α-D -ribo-hexofuranose and of some C(3′)-mono- and -disubstituted derivatives have been investigated. Deuterium labelled molecules allow fragmentation modes to be proposed. 相似文献