Showing papers by "Chung Yuan Christian University published in 1986"

Thermomechanically coupled non-linear vibration of plates☆

Abstract: An analytical method is presented for the analysis of large amplitude thermomechanically coupled vibrations of rectangular elastic thin plates with various boundary conditions. The field of temperature and deformation are assumed to be coupled, and the transverse and longitudinal deformations are mutually dependent. The fundamental equations of non-linear flexural vibration of a plate stemming from Berger's analysis are coupled with the energy equation. Based on one-term approximate solution technique, the system of non-linear equations is solved by employing the methods of Galerkin and successive approximations. The analytical solutions are compared with those for the linear case and from the numerical analysis to investigate the influence of thermomechanical coupling and large amplitude on the period of plate lateral vibration.

Helium flux in a continental land area estimated from 3He/4He ratio in northern Taiwan

Abstract: The helium flux and its isotopic composition may provide useful information not only on the helium budget in the atmosphere but also on the uranium and thorium contents of the rocks in the Earth's crust and mantle and the generation of heat from radioactive decay of these elements. Data have been available from oceanic areas1–4, but those from continental areas are sparse5–7. We report here the 3He and 4He fluxes derived from measurement of the 3He/4He ratio of natural gases in the northern part of Taiwan. The estimated 3He and 4He fluxes are 3.9 and 2.7 × 106 atoms cm−2 s−1 at the Chinshui site, and 7.2 and 2.4 × 106 atoms cm−2 s−1 at the Chuhuangkeng site. The 3He fluxes are in approximate agreement with the global flux estimated from excess 3He in sea water1. The 4He fluxes are comparable to the 4He flux6 for the continents deduced from terrestrial heat flow data and the heat/He flux ratio, but are significantly larger than those reported for the ocean floor. The relationship observed between the He isotope ratio and CO2 and CH4 concentrations suggests that there is a mixing trend between the high 3He/4He-high CO2-low CH4 component and the low 3He/4He-low CO2-high CH4 component. The former may be derived from the upper mantle and the latter produced in a sedimentary environment.

Phase Shifting Holographic Interferometry (PSHI)

Abstract: A digital phase shifting technique capable of quantitatively determining the phase of holographic interferometric fringes is presented. This technique uses computer control to take data and to calculate phase. The phase value at each detector point can be calculated by taking four successive intensity data frames with the reference phase shifted between each frame. The amount of phase shift introduced by this technique is unimportant. Theoretical analysis and experimental systems are described. Experiments are made in beam deflection measurements, holographic nondestructive testing and surface contouring of diffuse object to show the versatile applications of this technique.

Creep buckling of nonlinear viscoelastic columns

Abstract: Creep buckling of columns is analyzed for materials obeying nonlinear single memory integral constitutive laws. There have been two basic methods to analyze creep buckling of columns; the Rabotnov and Shesterikov's linearized dynamical approach and Hoff's quasistatic nonlinear approach, the former predicts critical buckling loads and the latter yields critical buckling times. The two theories are generally believed to be independent of each other. Through investigation of creep phenomena other than steady creep, the two different creep stability criteria are found to be correlated and thus the linear treatment is justified by a nonlinear approach. It is also shown that the Hoff's approach can be used to derive critical creep buckling loads. The missing link between the two theorees is found in this paper.

The Possibility of Using Disulfonated Cosurfactant for Enhanced Oil Recovery

Abstract: This paper will present a view on the use of a disulfonated surfactant to increase electrolyte tolerance of petroleum sulfonate at medium temperature. A series of thermally stable and commercially available disulfonate, Dowfax, was used with petroleum sulfonate for enhanced oil recovery. Laboratory experiments were carried out with the Dowfax-petroleum sulfonate systems at temperature around 70–75°C under different conditions. Good oil recovery was obtained in Berea sandstone cores with short slug injection against highly saline synthetic field water. Sulfonate loss is around 0.05 meq/100 g rock which is typical for Berea Sandstone. For reservoir application, more experiments are required.

Elasto-plastic large displacement analysis of cable systems

Abstract: A nonlinear finite element procedure for cable system analysis is presented in this paper. Both geometrical and material nonlinearities are taken into account. The nonlinear stress‐strain relationship proposed by Jonatowski and Birnstiel is adopted for describing the elasto‐plastic behavior of cable material. The ultimate carrying capacity and inelastic structural behavior of several cable systems are examined in this study. Conditions of loading, unloading and reloading, slackness and rupture of cable are also discussed. For nonlinear computation, the Newton‐Raphson method is utilized. A stable, fast computation algorithm with two iteration loops (elastic solution loop and material loop) is set up for large displacement elasto‐plastic analysis of cable systems. Numerical results show good agreement with previous studies.

Conformational Studies on Polytripeptides as a Model of Collagen

Abstract: To study the role of glycine residues in stabilizing the collagen triple helix, the glycine residues in the polytripeptide (Pro-Ala-Gly)n were partially replaced by alanine. The proline content was kept constant. The stability of the helical conformation of these polypeptides was studied by IR- and X-ray measurements in the solid state and by ORD, CD and viscometry in solution. The renaturation was followed as a function of time. All the polytripeptides studied, with the exception of (-Pro-Ala-Ala-)n attained the polyproline II conformation. However the stability decreased with increasing alanine content. Obviously the molecules of (-Pro-Ala-Gly-) are highly associated by intermolecular hydrogen bonds and one may therefore suppose that a triple-stranded helix aggregation occurs. The results of the refolding process show that the stability of the helices seems to also affect the refolding rate in terms of the optical rotation, Two transitions appeared: the first one is responsible for a rapid reversible change in conformation and the second one for a further slow and irreversible change in the hydrodynamic shape. The latter seems to be due to the partial helical nature, leading to higher chain mobility.

The Reaction of 2,5‐Dimethoxy‐2,5‐Dihydrofuran with Dichloroketene

Abstract: 2,5-Dimethoxy-2,5-dihydrofuran (DDF) reacts with dichloroketene to give 7,9-dimethoxy-3,3,5,5-tetrachloro-8-oxabicyclo[4,3,0]-noan-2,4-dione (I), and methyl chloro-(2,5-dihydro-5-methoxy-2-furanylidene) acetate (II). The reactions of 2,5-dihydrofuran and 2,5-dimethoxy-tetrahydrofuran with dichloroketene were also-studied for comparison. Compound II was derived from the insertion of a molecule of dichloroketene into the C-O bond of DDF with subsequent dehydrochlorination. Compound I resulted from the cycloaddition of two molecules of dichloroketene to the C=C bond of DDF. A mechanism involving a 1,5-dipolar intermediate is proposed to account for this novel reaction.