Superposition Analysis Research Articles

On a method for vibration analysis of viscous compressible fluid–structure systems

AbstractA fluid–structure interaction formulation for viscous compressible fluid is under consideration. The formulation involves finite element approximation of linearized Navier–Stokes equations and response determination made by means of modal superposition analysis. Standard and simplified schemes of the viscous compressible fluid–structure interaction problem solution are developed. The schemes are based on the frequency condensation method of a complex eigenvalue problem solving. Free and forced oscillations of several fluid–structure systems are studied by the standard and simplified schemes. The analysis of the results obtained shows that the simplified scheme provides a saving of 90% of the computational time required to define oscillation of the structure with viscous compressible fluid in the lowest frequency range. A certain influence of the fluid viscosity on the transient response of the fluid–structure system is also demonstrated. Copyright © 2004 John Wiley & Sons, Ltd.

Generation of AuPd22/Au2Pd21 analogues of the high-nuclearity Pd23(CO)20(PEt3)10 cluster containing 19-atom centered hexacapped-cuboctahedral (nu 2-octahedral) metal fragment: structural-to-synthesis approach concerning formation of Au2Pd21(CO)20(PEt3)10.

Reactions of Pd(PEt(3))(2)Cl(2) and Au(PPh(3))Cl in DMF with NaOH under CO atmosphere gave rise to the unique capped three-shell homopalladium Pd(145)(CO)(x)(PEt(3))(30)(x approximately 60) and two neutral Au-Pd clusters: Au(2)Pd(21)(CO)(20)(PEt(3))(10) (1) and Au(2)Pd(41)(CO)(27)(PEt(3))(15)(following article). Similar reactions with Pd(PMe(3))(2)Cl(2) being used in place of Pd(PEt(3))(2)Cl(2) afforded Au(2)Pd(21)(CO)(20)(PMe(3))(10) (2), the trimethylphosphine analogue of, and the electronically equivalent [AuPd(22)(CO)(20)(PPh(3))(4)(PMe(3))(6)](-) monoanion (3) as the [PPh(4)](+) salt. Each of these three air-sensitive 23-atom heterometallic Au-Pd clusters was obtained in low yields (7-25%); however, their geometrical similarities with the known cuboctahedral-based homopalladium Pd(23)(CO)(20)(PEt(3))(10) (4), recently obtained in good yields from Pd(10)(CO)(12)(PEt(3))(6), suggested an alternative preparative route for obtaining. This "structure-to-synthesis" approach afforded 1 in 60-70% yields from reactions of Pd(10)(CO)(12)(PEt(3))(6) and Au(PPh(3))Cl in DMF with NaOH under N(2) atmosphere. Both the compositions and atomic arrangements for 1, 2 and 3 were unambiguously established from low-temperature single-crystal CCD X-ray crystallographic determinations in accordance with their nearly identical IR carbonyl frequencies. Cluster 1 was also characterized by (31)P[(1)H] NMR, cyclic voltammetry (CV) and elemental analysis. The virtually identical Au(2)Pd(21) core-architectures of 1 and 2 closely resemble that of 4, which consists of a centered hexa(square capped)-cuboctahedral Pd(19) fragment of pseudo-O(h) symmetry that alternatively may be viewed as a centered Pd(19)nu(2)-octahedron (where nu(n) designates (n + 1) equally spaced atoms along each edge). [AuPd(22)(CO)(20)(PPh(3))(4)(PMe(3))(6)](-) (3) in the crystalline state ([PPh(4)](+) salt) consists of two crystallographically independent monoanions 3A and 3B; a superposition analysis ascertained that their geometries are essentially equivalent. A CV indicates that reversibly undergoes two one-electron reductions and two one-electron oxidations; these reversible redox processes form the basis for an integrated structural/electronic picture that is compatible with the existence of the electronically-equivalent 1-3 along with the electronically-nonequivalent 4 (with two fewer CVEs) and other closely related species.

Melt Rheology of Thermoplastic Elastomers from High Density Polyethylene/Styrene – Butadiene Rubber Blends: Effect of Blend Ratio and Dynamic Vulcanization

The melt rheological behavior of HDPE/Styrene butadiene Rubber blends has been investigated with special reference to the effect of blend ratio, shear stress and temperature using capillary rheometer. HDPE/SBR blends show pseudoplastic behavior, which evidenced by the decrease in viscosity with increase in shear rate. The flow behavior index also support the pseudoplastic nature of these blends. The viscosity of the blends increase as the amount of SBR increases. The shear viscosity versus composition of the blends showed negative deviation, which is more pronounced at low shear rates. Various theoretical models are used to predict the melt viscosity of the blends. The influence of dynamic crosslinking using different curing systems on the rheological properties of the blends has been analyzed. A shear-rate superposition analysis has been done to predict the melt viscosities of the system as a function of temperature. Using a plot of modified shear stress versus shear rates; it is seen that various curves were unified as a single master curve.

Simplified Analysis of Heat-Curved Steel Girders

Heat curving is commonly used in the fabrication of curved structural steel bridge girders. A two-dimensional superposition analysis known as the Duhamel Analogy was used for numerical modeling in the development of the AASHTO code provisions. This iterative analysis can take into consideration multiple heating–cooling cycles, initial residual stresses, temperature-dependent material properties, and the nonlinear temperature distribution across the girder cross section. A simplified analysis based on the Duhamel Analogy that can be carried out by using hand calculations is described. The curvatures obtained by this method are within 15% of the measured curvatures, which are very comparable to the results obtained by using the Duhamel Analogy or the three-dimensional, nonlinear, finite element solution. The background, basis, and steps required for the proposed analysis are described; and an illustrative numerical example is presented. The proposed analysis may be used to estimate curvatures or to determine the maximum fabrication temperature and the heating width for a single heating–cooling cycle for steels such as high-performance steel not covered by the current AASHTO provisions.

Condition monitoring of a thermally aged elastomer by 1H‐NMR T2 relaxation measurements of solvent‐swelled samples

AbstractThe aging of polymers is often monitored by mechanical property measurements such as those of Young's modulus or tensile elongation at break; new methods are required, however, in situations where traditional mechanical methods cannot be employed. A hydroxy‐terminated polybutadiene/isophorone diisocyanate elastomer is commonly used as a propellant binder. The thermal degradation of the binder is believed to be an important parameter governing the performance of the propellant. Classical mechanical methods cannot be used to monitor the condition of this material when it has been aged in situ as a highly dispersed binder. In this study, the 1H‐NMR spin‐spin relaxation times, T2, of solvent‐swelled samples decreased substantially as thermally induced oxidation led to additional crosslinking. A time–temperature superposition analysis of the relaxation times was performed on samples that had been aged at temperatures ranging from 50 to 125°C. The acceleration factors derived from the relaxation measurements agreed with those reported earlier for tensile elongation at break and oxygen consumption. The dependence of T2 on tensile elongation at break was independent of the temperature at which the sample was aged. A shortened version of the experiment, requiring only two spin‐echo delay times, is presented. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3636–3641, 2002

Force field superposition analysis of three-dimensional stress concentrations

The force field superposition method for linear elastic problems of stress analysis involves representing the stress field in a given solution domain as a superposition of fields generated by a number of point forces. These forces are located outside the solution domain, which can be infinite in extent. Previous work on two-dimensional applications has shown that remarkable accuracy can be achieved, particularly for certain types of stress concentration problems. This paper explores the application of force field superposition to three-dimensional stress concentrations, particularly those associated with holes through, and cavities within, components under various types of loading.

Trade typhoon over Japan: Turbulence metaphor and spatial production cycles feedback loops of the Japanese economy, 1980–85–90

This paper deals with the turbulence similitude between whirlpool structure of atmosphere disturbances and the spatial production cycles. Such an analogy leads to the production cycles feedback loops superposition analysis of trade feedbacks reflecting the economic phenomena of horizontal and vertical trade specifications. Moreover, the visualization of this process is achieved with the help of coloring the different permutation matrices presenting the hierarchy of production cycles feedback loops. In this manner the qualitative presentation of Japan inter‐regional and inter‐industry trade, 1980–85–90, is visualized and interpreted.

Changes in cloud cover associated with Forbush decreases of galactic cosmic rays

The results of a study to quantify the relationship between cloud cover and short‐term Forbush decreases (FD) of galactic cosmic ray flux are presented. Using an extensive record of global satellite‐derived cloud products from the International Satellite Cloud Climatology Project (ISCCP) D1 data series, epoch superposition analysis of a sample of FD events is conducted. This analysis is conducted at a range of spatial scales from global, through 5° geomagnetic latitude bands to a global grid with 2.5° resolution. Resulting cloud anomalies are tested for significance using a randomized Monte Carlo experiment. The results indicate a small but significant (at 0.001 probability level) decline in the global proportion of cloud cover (of up to 1.4%) immediately prior to and following FD events. Analysis of data averaged over geomagnetic latitude (φ) bands reveals that significant cloud anomalies are concentrated in the high latitudes. A substantial (small) decline in cloud cover occurs at Southern (Northern) Hemisphere polar latitudes and is accompanied by a small but significant increase near φ = 30°N. The high‐latitude anomalies occur largely in the high‐level cloud and are particularly pronounced (up to −30%) in the uppermost cloud (occurring at 10–180 mbar) over Antarctica. In contrast, analysis using a sample of FD events associated with solar proton events shows no statistically significant cloud anomalies. A discussion of possible explanations of the results is provided.

Household and Family at Moche, Peru: An Analysis of Building and Residence Patterns in a Prehispanic Urban Center

The Moche was the last complex society to develop on the Peruvian north coast during the Early Intermediate Period (200 B. C.-700 A. D.). While archaeological research on the Moche has traditionally concentrated on the impressive marks of political and religious power, we know relatively little about Moche household organization and patterns of residence. In this research, conducted at the eponymous site of Moche, I identify three types of architectural organization relating to both residential and nonresidential spaces. An analysis of building materials and architectural superposition suggests a close relationship among construction quality, household size, and occupational continuity, in the case of residential architecture. The observed differences, I argue, reflect strategies of household social reproduction among Moche's urban population that depend largely on socioeconomic status. I also contend that different forms of labor were responsible for the construction of residential compounds and other specialized areas, the function of which may not be primarily residential. This research emphasizes the great potential of studying domesticity in prehistory as well as the dynamics of urban construction and suggests methods effective for the reconstruction of household forms and change in sedentary societies.

Constructing Conformationally Constrained Macrobicyclic Musks

To investigate the structure-odor correlation of musks, (12R)-12-methyl-13-tridecanolide (1), a macrocyclic musk, and 13-tridecanolide, its non-musky demethyl analogue, were conformationally constrained by introduction of methylene bridges between C-3 and C-8 or C-9. These [7.5.1]- and [8.4.1]-macrobicycles were synthesized starting from bicyclo[5.3.1]undec-8-en-9-one (3) and bicyclo[4.3.1]dec-7-en-8-one (8), respectively, by a sequence consisting of catalytic hydrogenation, alpha-alkylation with a TBS-protected (tert-butyldimethylsilyl) hydroxy halide, acid-catalyzed cyclization, oxidative cleavage of the formed enol ether double bond, and subsequent reduction of the carbonyl group via its tosylhydrazone. The compound (1R,6R,9R)-(+)-6-methyl-4-oxa-bicyclo[7.5.1]pentadecan-3-one (22) was found to possess the most pronounced musk odor, and this was rationalized by a superposition analysis with the polycyclic aromatic musk odorant (4S,7R)-Galaxolide (2). In its (1S,6R,9S)-(+)-stereoisomer 23 as well as in (1S,6R, 10R)-(+)-6-methyl-4-oxabicyclo[8.4.1]-pentadecan-3-one (18) the (6R)-methyl group seems to hinder the interaction with the musk receptor, while the demethyl compounds 7 and 12 showed only very faint odors.

Constructing conformationally constrained macrobicyclic musks.

To investigate the structure-odor correlation of musks, (12R)-12-methyl-13-tridecanolide (1), a macrocyclic musk, and 13-tridecanolide, its non-musky demethyl analogue, were conformationally constrained by introduction of methylene bridges between C-3 and C-8 or C-9. These [7.5.1]- and [8.4.1]-macrobicycles were synthesized starting from bicyclo[5.3.1]undec-8-en-9-one (3) and bicyclo[4.3.1]dec-7-en-8-one (8), respectively, by a sequence consisting of catalytic hydrogenation, alpha-alkylation with a TBS-protected (tert-butyldimethylsilyl) hydroxy halide, acid-catalyzed cyclization, oxidative cleavage of the formed enol ether double bond, and subsequent reduction of the carbonyl group via its tosylhydrazone. The compound (1R,6R,9R)-(+)-6-methyl-4-oxa-bicyclo[7.5.1]pentadecan-3-one (22) was found to possess the most pronounced musk odor, and this was rationalized by a superposition analysis with the polycyclic aromatic musk odorant (4S,7R)-Galaxolide (2). In its (1S,6R,9S)-(+)-stereoisomer 23 as well as in (1S,6R, 10R)-(+)-6-methyl-4-oxabicyclo[8.4.1]-pentadecan-3-one (18) the (6R)-methyl group seems to hinder the interaction with the musk receptor, while the demethyl compounds 7 and 12 showed only very faint odors.

A force field superposition approach to plane elastic stress and strain analysis

The force field superposition method for linear elastic problems of stress and strain analysis involves representing the stress and displacement fields in a given solution domain as a superposition of fields generated by a number of point forces. These forces are located outside the solution domain, and in the case of two-dimensional, singly connected finite domain problems can be uniformly distributed around the perimeter of a circle enclosing the physical domain. Doubly connected and infinite domain problems can also be treated. The results of some simple test problems show that remarkable accuracy can be achieved with very little computational effort relative to other numerical methods. More complex problems require the solution domain to be divided into several subdomains, each of which may be subjected to superposition analysis.

III. Geometrical optics of variable-frequency light rays in the general relativistic regime: Combined gravitational and refractive lensing

The frequency-sensitive extremum principle for propagation of light rays in the geometrical optics regime is used to develop a nonperturbative method for tracing light rays in a transparent refractive medium in the general relativistic environment. The general formulation of the theory is given first; it allows for the numerical analysis of a nonlinear superposition of gravitational and refractive lensing, when neither of the two effects can be treated as a small perturbation. The scope of the general theory is gradually narrowed to the Schwarzschild field, the spherical symmetry of the refractive properties of the medium, and the small deflection regime approximation. A simple, analytically solvable example of deflection of light rays by a mass embedded in a refractive medium is considered in detail; in a vacuum, deflection of light rays by the Sun is reproduced.PACS Nos.: 42.15-i, 04.20-q, 98.90+s

Analysis of Hydroperoxides in Solid Polyethylene by MAS 13C NMR and EPR

13C-enriched polyethylene was subjected to γ-irradiation in the presence of air at 25 and 80 °C for total doses ranging from 71 to 355 kGy. Significant quantities of hydroperoxides were detected in the 25 °C irradiated sample by 13C magic angle spinning NMR spectroscopy. This method of detection was performed on the solid polymer and required no chemical derivatization or addition of solvent. The chemical stability and subsequent products of the hydroperoxide species were studied by annealing the irradiated samples in air at temperatures ranging from 22 to 110 °C. A time−temperature superposition analysis provided an activation energy of 108 kJ/mol for the hydroperoxide decomposition process. The primary products of hydroperoxide decomposition were ketones and secondary alcohols with lesser amounts of acids and esters. EPR measurements suggest that the reactive hydroperoxide species reside in the amorphous phase of polyethylene, consistent with degradation occurring in the amorphous phase.

Microstructures in CoPtC magnetic thin films studied by superpositioning of micro-electron diffraction

Cross-sectional transmission electron microscopy observation of CoPtC thin films showed that 10 nm sized ultrafine particles of CoPt typically were elongated along the substrate normal. Analysis of the superposition of 40 micro-electron diffraction patterns showed that there was no preferred crystal orientation of CoPt particles. This superpositioning technique can be applied to thin films, whose X-ray diffraction analysis is difficult due to the small size of the crystals.

Morphology and mechanical and viscoelastic properties of natural rubber and styrene butadiene rubber latex blends

The morphology and mechanical and viscoelastic properties of a series of blends of natural rubber (NR) and styrene butadiene rubber (SBR) latex blends were studied in the uncrosslinked and crosslinked state. The morphology of the NR/SBR blends was analyzed using a scanning electron microscope. The morphology of the blends indicated a two phase structure in which SBR is dispersed as domains in the continuous NR matrix when its content is less than 50%. A cocontinuous morphology was obtained at a 50/50 NR/SBR ratio and phase inversion was seen beyond 50% SBR when NR formed the dispersed phase. The mechanical properties of the blends were studied with special reference to the effect of the blend ratio, surface active agents, vulcanizing system, and time for prevulcanization. As the NR content and time of prevulcanization increased, the mechanical properties such as the tensile strength, modulus, elongation at break, and hardness increased. This was due to the increased degree of crosslinking that leads to the strengthening of the 3-dimensional network. In most cases the tear strength values increased as the prevulcanization time increased. The mechanical data were compared with theoretical predictions. The effects of the blend ratio and prevulcanization on the dynamic mechanical properties of the blends were investigated at different temperatures and frequencies. All the blends showed two distinct glass-transition temperatures, indicating that the system is immiscible. It was also found that the glass-transition temperatures of vulcanized blends are higher than those of unvulcanized blends. The time-temperature superposition and Cole-Cole analysis were made to understand the phase behavior of the blends. The tensile and tear fracture surfaces were examined by a scanning electron microscope to gain an insight into the failure mechanism.

Earthquake amplification factors for self-supporting telecommunication towers

In the absence of specific guidelines for the seismic analysis of self-supporting telecommunication towers, designers may be tempted to apply building-code approaches to these structures. However, these towers respond to earthquakes in a different fashion than shear buildings. In this study, earthquake amplification factors for the base shear and the total vertical reaction of self-supporting latticed telecommunication towers are suggested based on modal superposition analysis performed on 10 existing towers, each being subjected to a set of strong-motion accelerograms acting in the horizontal and the vertical directions separately. Results are presented in detail for two of the towers studied, with heights of 66 and 121 m, respectively. Simple regression analyses are performed on the results from which the base shear and vertical reaction amplification factors are found. These factors are presented as functions of the tower's largest flexural period or largest axial period of vibration as appropriate, and can be used by designers to estimate the expected level of dynamic forces developed in self-supporting telecommunication towers due to an earthquake.Key words: dynamic analysis, lattice towers, base shear, vertical reaction.

Seismic vulnerability evaluation of a 32-story reinforced concrete building

Seismic evaluation of a 32-story reinforced concrete framed tube building is performed by checking damageability, safety, and toughness limit states. The evaluation is based on Standard 2800 (Iranian seismic code) which recommends equivalent lateral static force, modal superposition, or time history dynamic analysis methods to be applied. A three dimensional linearly elastic model checked by ambient vibration test results is used for the evaluation. Accelerograms of three earthquakes as well as linearly elastic design response spectra are used for dynamic analysis. Damageability is checked by considering story drift ratios. Safety is evaluated by comparing demands and capacities at the story and element force levels. Finally, toughness is studied in terms of curvature ductility of members. The paper explains the methodology selected and various aspects in detail.

An accurate method for measurement of transverse elastic-wave velocities

We demonstrate a novel analysis that improves the accuracy of angle-dependent elastic-wave velocities in plates for water-immersion measurements. Water-immersion measurements utilize the conversion from longitudinal to transverse mode to determine the velocities of transverse waves. However, beyond the critical angle for longitudinal waves, the phase of the transmitted transverse waves is affected by the presence of evanescent longitudinal waves at the interface. With pulse superposition analysis this effect systematically decreases the apparent velocities at some angles. Previous researchers have corrected the apparent velocities by calculating the theoretical phase shift from known parameters, but this correction requires narrow-band pulses or tone bursts as well as estimations of these parameters. An advantage of our analysis is that it eliminates the need for a priori estimations of parameters. In addition, this analysis allows the use of broad-band pulses that are more applicable to thin plates. To demonstrate these advantages, measurements were conducted on an isotropic steel plate as it was rotated in an immersion tank and insonified with a broad-band ultrasonic transducer. We compared velocities determined by the pulse-echo superposition analysis with velocities determined by our analysis. As expected, there was no significant difference between the longitudinal velocities, but systematic variations in the transverse velocities were lower with this new method.

An example of mixed carbonate–pyroclastic sedimentation (Miocene, Central Basin, Iran)

Depositional environments of the f-Member of the Qum Formation, in the Central Basin of Iran, have been reconstructed by two approaches: (1) a detailed petrographic analysis of microfacies (MF); (2) an analysis of the vertical superposition of the microfacies using contingency tests. Both approaches reveal a vertical sequence of eight microfacies designated by letters A–H. Based on petrographic characteristics and environmental significance the studied MF were interpreted in terms of depositional environments as follows: MF-A (basin); MF-B (lower slope); MF-C (reef flank); MF-D (proximal talus); MF-E (organic reef); MF-F (lagoon); MF-G (restricted marine shoal); MF-H (restricted shelf). The f-Member carbonates were deposited in shallow-water high-energy conditions mostly as reef and fore-reef facies. Carbonate deposition took place on a carbonate ramp under conditions of periodic to almost continuous influx of pyroclastic material. The presence of pyroclastic material throughout the studied sections indicates that at the time of deposition an island-arc volcanic complex was active nearby. The absence of a wide range of typical lagoonal facies indicates that reefal facies developed as a narrow elongated strip close to the shoreline. The immediate increase in depth off the reef edge prevented its seaward expansion, because the volume of the produced reef talus material was insufficient to provide a shallow foundation for seaward expansion. The sedimentary build-up of the f-Member at the studied area evolved from fringing reef to barrier reef through time and space.