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81.
We consider the statistical mechanics of the traveling salesman problem (TSP) and develop some representations to study it. In one representation the mean field theory has a simple form and brings out some of the essential features of the problem. It shows that the system has spontaneous symmetry breaking at any nonzero temperature. In general the phase progressively changes as one decreases the temperature. At low temperatures the mean field theory solution is very sensitive to any small perturbations, due to the divergence of some local susceptibilities. This critical region extends down to zero temperature. We perform the quenched average for a nonmetric TSP in the second representation and the resulting problem is more complicated than the infinite-range spin-glass problem, suggesting that the free energy landscape may be more complex. The role played by frustration in this problem appears explicitly through the localization property of a random matrix, which resembles the tight binding matrix of an electron in a random lattice. 相似文献
82.
Zusammenfassung Eine ausgeprägte Strangaufweitung tritt bei anorganischen Glasschmelzen dann auf, wenn bei schleichender Strömung eine Haftung zwischen der Wand des Matrizenkanals und dem strömenden Medium gegeben ist. Sie rührt dabei von der Umorientierung der Geschwindigkeitsverteilung von einem parabelförmigen zu einem kastenförmigen Profil her.In den experimentellen Untersuchungen konnte festgestellt werden, daß oberhalb einer bestimmten Kanallänge, d. h. bei ausgeprägten Strömungsverhältnissen im Preßwerkzeug die flächenbezogene Strangaufweitung konstant und dabei insbesondere unabhängig von der Profilform etwa 29% beträgt. Daraus wird gefolgert, daß dieser Betrag dem linearen Wert für den zweidimensionalen Fall des unendlich ausgedehnten Spaltes entsprechen muß.In einer theoretischen Analyse wurde die Berechnung dieses Falles ausgehend von der Stokes-Gleichung mit Hilfe der Methode der finiten Elemente durchgeführt. Aus der sich daraus ergebenden Druck- und Geschwindigkeitsverteilung konnte schließlich die Kontur des austretenden Stranges sowie dessen Endhöhe ermittelt werden.Ein Vergleich der experimentell und rechnerisch ermittelten Werte für die Strangaufweitung zeigt dabei eine recht gute Übereinstimmung und bestätigt dadurch auch die weitgehende Unabhängigkeit der flächenbezogenen Aufweitung von der Querschnittsform des Stranges.
A Fläche - a p ,a u Knotenpunktsvariablen für Druck bzw. Geschwindigkeit - a, b Seitenlängen des Rechteckprofils - B =L · N u Matrix - D Viskositätsmatrix - f Kräftematrix - K Schwerkraftvektor - K p ,K u Elementdruckmatrix, Elementgeschwindigkeitsmatrix - L Transformationsmatrix für den ebenen Fall - m Kronecker-Symbol für den zweidimensionalen Strömungszustand - N p ,N u Ansatzfunktionsmatrizen für Druck bzw. Geschwindigkeit - p Preßdruck - R Radius - T Preßtemperatur - t Lastvektor - u = (w, v) Geschwindigkeitsvektor - A flächenbezogene Strangaufweitung - R Aufweitung einer linearen QuerschnittsabmessungR - dynamische Viskosität - Dichte - D u/Dt Substantielle Ableitung der Geschwindigkeit nach der Zeit - T Transponierte einer Matrix (oberer Index) Vorgetragen auf der Jahrestagung der Deutschen Rheologischen Gesellschaft in Berlin vom 13.–15. Mai 1985 相似文献
Inorganic glass melts are showing a characteristic die swell, when in the case of slow motion a strong adhesion between the streaming fluid and the wall of the die channel exists. The reason for this phenomenon is the rearrangement of the velocity profile from a parabolic to a box-type design form.The experimental investigations have demonstrated, that above a certain channel length, this means at distinct flow conditions inside the die channel, the value for the extension of the cross-sectional area is constant of about 29%. Particularly it is independent of the shape of the used die profiles. From this result, it is to deduce that this value must correspond to that of the two-dimensional case of the infinite extended slit.In a theoretical analysis the computation of this case was performed, starting from the Stokes-equation by the finite element method. By means of the resulting pressure and velocity distribution, the contour of the emerging rod and its final thickness could be determined.A comparison between experimental and computational results shows good agreement. So the appreciable independence of the magnitude of the die swell from the profile of the extruded rod is confirmed.
A Fläche - a p ,a u Knotenpunktsvariablen für Druck bzw. Geschwindigkeit - a, b Seitenlängen des Rechteckprofils - B =L · N u Matrix - D Viskositätsmatrix - f Kräftematrix - K Schwerkraftvektor - K p ,K u Elementdruckmatrix, Elementgeschwindigkeitsmatrix - L Transformationsmatrix für den ebenen Fall - m Kronecker-Symbol für den zweidimensionalen Strömungszustand - N p ,N u Ansatzfunktionsmatrizen für Druck bzw. Geschwindigkeit - p Preßdruck - R Radius - T Preßtemperatur - t Lastvektor - u = (w, v) Geschwindigkeitsvektor - A flächenbezogene Strangaufweitung - R Aufweitung einer linearen QuerschnittsabmessungR - dynamische Viskosität - Dichte - D u/Dt Substantielle Ableitung der Geschwindigkeit nach der Zeit - T Transponierte einer Matrix (oberer Index) Vorgetragen auf der Jahrestagung der Deutschen Rheologischen Gesellschaft in Berlin vom 13.–15. Mai 1985 相似文献
83.
The gas-phase photocatalytic oxidation of aniline on a new kind of porous nano-TiO2 composite films is investigated. The composite film was prepared on glass fiber with the water glass as binders and dilute
H2SO4 solution as solidifying reagent. The surface characters were observed by scanning electron microscope. The photocatalytic
degradation of aniline on the composite films was carried out in a TiO2/UV system. Some important factors affecting the photodegradation, such as the concentration of TiO2, the initial concentration of aniline, and the existing water vapor, are also studied. The product of photocatalytic oxidation
was detected by Fourier transform-Infrared. The partial intermediate products were absorbed on TiO2 surface, which resulted in catalyst deactivation. But when it was irradiated under UV illumination or solar irradiation for
some time, the catalyst could be reused without loss of catalytic activity.
Translated from the Journal of Wuhan University (Natural Science Edition), 2005, 51(2) (in Chinese) 相似文献
84.
手性液晶聚硅氧烷毛细管柱的制备及应用 总被引:3,自引:0,他引:3
合成了一种手性液晶侧链的聚硅氧烷固定液,并涂制成毛细管柱,此柱适合于分离各种取代基的酚类异构体。对柱效和选择性进行了评价。 相似文献
85.
Intramolecular cyclization of 1-amino-3-phenacyl-4-carbohydrazido-1,2,3-triazolium-5-olates has been shown to take place via selective interaction of the carbonyl group with the terminal amino function of the hydrazido group to form a 1,2,5-triazepine ring. Minor products, resulting from the interaction of the α-nitrogen atom of the hydrazido group with the carbonyl function, having a N-amino-pyridazine structure were also detected and isolated. A general method for the synthesis of novel mesoionic 2-amino-7-aryl-4-oxo-2,4,5,8-tetrahydro[1,2,3]triazolo[5,1-d][1,2,5]triazepin-9-ium-3-olates was developed. 相似文献
86.
Miyasaka M Rajca A Pink M Rajca S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(24):6531-6539
Synthesis of thiophene-based [7]helicenes, which are functionalized for both design of organic chiral glasses with strong chiroptical properties and for further homologation to higher [n]helicenes, is reported. The key synthetic transformations are kinetic resolution of the intermediate diketone and the annelation step forming the center benzene ring by means of an intramolecular McMurry reaction. Based upon X-ray crystallographic determinations of the absolute configurations for (+)-enantiomers of the diketone and the [7]helicene, stereochemical correlation between the (R) axial chirality of the diketone and the (M) helical chirality of the [7]helicene is established. One such enantiopure trimethylsilyl-substituted [7]helicene possesses enchanced chiroptical properties and forms a chiral molecular glass. 相似文献
87.
Two protocols for functionalization of glass supports with hexaethylene glycol (HEG)-linked oligonucleotides were developed.
The first method (standard amidite protocol) made use of the 2-cyanoethyl-phosphoramidite derivative of 4,4′-dimethoxytrityl-protected
HEG. This was first coupled to the support by standard solid-phase phosphoramidite chemistry followed by extension with a
thymidylic acid icosanucleotide. Stepwise addition of the linker phosphoramidite graduated at 1% (relative to the total sites
available) perstep at 50°C resulted in an optimal yield of immobilized oligonucleotides at a density of 2.24 × 1010 strands/mm2. This observed loading maximum lies well below the theoretical maximum loading owing to nonspecific adsorption of HEG on
the glass and subsequent blocking of reactive sites. Surface loadings as high as 3.73 × 1010/mm2 and of excellent sequence quality were achieved with a reverse amidite protocol. The support was first modified into a 2-cyanoethyl-N,N-diisopropylphosphoramidite analog followed by coupling with 4,4′-dimethoxytrityl-protected HEG. This protocol is conveniently
available when using a conventional DNA synthesizer. The reverse amidite protocol allowed for control of the surface loading
at values suitable for subsequent analytical applications that make use of immobilized oligonucleotides as probes for selective
hybridization of sample nucleic acids of unknown sequence and concentration. 相似文献
88.
Cédric Kalinski Michael Umkehrer Nadine Jäger Wolfgang Hiller 《Tetrahedron letters》2006,47(12):2041-2044
A combinatorial synthetic route yielding fused tetrazolo[1,5-a]quinoxalines is described. The use of 2-fluorophenylisocyanide in the Ugi-tetrazole reaction (tetrazole-U-4CR) followed by a nucleophilic aromatic substitution (SNAr) affords the tricylic tetrazolo[1,5-a]quinoxaline moiety in good yields and with high diversity. 相似文献
89.
K. Grob 《Journal of separation science》1978,1(5):263-267
During one year continuous use of on-column injection, the typical advantages described in our first report have fully been confirmed. In addition the analysis of large sample volumes has proved promising. Only minor modifications have been applied to the on-column injector device. Broad evidence has been gathered showing that full separation efficiency of the capillary columns after on-column injection is attained only when cold trapping or the solvent effect, as band shortening mechanisms, are working- While, under the conditions of on-column injection, cold trapping is less efficient than with other injection techniques, the opposite holds true for the solvent effect. Compared with splitless injection, the danger of excessive solvent condensation on the column is increased. A working rule is presented for establishing the optimal chromatographic conditions for handling large sample volumes while ensuring full separation efficiency yet avoiding harm to the column. 相似文献
90.
Atactic polystyrene, both side group and main chain deuterated, was investigated by inelastic neutron scattering in a wide temperature range around the glass transition from 2 to 450 K. In the glass the Boson peak position is only very weakly influenced by the deuteration of the phenyl group. In the neighborhood of the glass transition temperatureT
g we find a fast relaxation process similar to other glasses. The onset of the fast relaxation in polystyrene, however, is observed already at temperaturesT
g — 200 K. Results from partially deuterated polystyrene suggest a change of the phenyl ring dynamics already far belowT
g. 相似文献