Numerical studies using circular arch finite elements

The paper is concerned with the performance of curved-beam, finite element models of circular centre line in the solution of circular arch problems. Attention is concentrated on the selection of the assumed displacement patterns and the comparative efficiency of some relatively high-order, independently-interpolated models and of previously formula: ed models is investigated. Results of a number of applications are presented in the form of convergence curves for central displacement and of moment and force distributions throughout the arch. These results illustrate the great improvement which is gained by increasing the order of the assumed displacement components for independently-interpolated models from cubic to quintic.     

含有机酸的油田水中碳酸盐含量的确定

大多油田水中的可溶性有机酸，对测定水中碳酸盐含量有很大的影响，试验结果表明，当水中同时存在有机酸时，如用强酸滴定碳酸盐，用甲基红指示终点，则得到的碳酸氢含量将会高于实际值。     

Static analysis of diaphragm-supported cylindrical shells using a curved finite strip

Two versions are presented of a tranversely-curved finite strip for the static analysis of circular cylindrical shells. The strip is a refined displacement model with sixteen transverse degrees-of-freedom arranged either at two or at four nodal lines. The analysis is specialized for cylinders with diaphragm supports at the ends—via the employment of simple trigonometric series in the longitudinal direction—but extension to other end conditions is straightforward in principle. Detailed results of applications of the curved strip are presented.     

Immune response of channel catfish under different environmental conditions

Channel catfish were maintained under conditions of low (15.4 C) and fluctuating (15.4 to 26.9 C/24 hours) temperatures, low (126 mg/L NO3-N) and high (289 mg/L NO3-N) nitrate in recirculating systems, crowding (171 g body mass/L), and fasting. They were vaccinated with formalin-killed enteric red-mouth bacterium, and antibody titers were monitored weekly for 10 weeks. Only those fish maintained in low or fluctuating temperature environments had significant (P less than 0.01) immunosuppression. The other environmental conditions studies, which are commonly encountered in intensive fish culture operations, did not compromise the humoral immune response of channel catfish.     

WATER-SENSITIVITY AND MIGRATION OF FINES IN THE HOPEMAN SANDSTONE

Water-sensitivity tests have been performed on samples of the Triassic Hopeman Sandstone from Clashach Quarry near Elgin in Scotland. Despite the apparent lack of clay minerals in the samples, the permeability of core plugs to NaCl and KCl brines decreases with progressive volume of efflunent, and drops dramatically when distilled water is flushed through. The permeability to CalCl brines remains constant, however, emphasising the stabilsing effect of polyvalent cations. These results are explained by cation exchange, expansion of electric double layers and the consequent migration of fines.     

Determination of Dew Point Pressure With and Without a Visual Cell

The dew point pressure of a gas condensate fluid is used for planning the production profile of gas condensate reservoirs and for determining their economic success. Usually the best method of the determination of the dew point pressure loci is by visual observation when a constant mass expansion (CME) test is performed on a sample in a high-pressure cell fitted with a glass window. In this test the cell pressure is reduced in steps and the pressure at which the first sign of a liquid droplet is observed and is recorded as the dew point pressure. The gas volume of the saturated fluid at dew point pressure is used as a reference volume and the total hydrocarbon volume measured for each pressure depletion step is reported relative to this volume. For lean gas condensate systems the amount of heavy components that can condense during pressure reduction is less than 4 mol% (<50 bbls/MMscf). Such experimental determination of dew point pressure for these gases require many small pressure reduction steps which make the observation method tedious, time consuming, and expensive. In this study the authors demonstrate that a graphical method of determining dew point pressure, which does not require a windowed cell for visual observation is possible. The authors have extended the Y-function, which is often used to smooth out CME data for black oils to gas condensate systems. They started from the initial measured pressure and volume and by plotting log of the extended Y-function, which they call the Y_RRR-function, with the corresponding pressure so that two straight lines were obtained: one above and one below the dew point. The point at which these two lines intersect is the dew point pressure. The Y_RRR-function method was applied to determine the dew point pressure for both a lean and a rich gas condensate system. The difference between the dew point pressures determined by the authors’ proposed Y_RRR-function method and the observation method was less than ±2.0% for both gas systems. This extension of the Y-function to determine dew point pressure was not found elsewhere in the open literature.     

激光的基本特征是高光子简并度

本文提出了激光基本特征的新观点，认为它可以统一关于在这个问题上的不同看法。     

1.2 Gbit/s fully integrated transimpedance optical receiver OEIC for 1.3-1.55 mu m transmission systems

The design and performance characteristics of a 1.2 Gbit/s transimpedance receiver OEIC incorporating a high voltage gain, low input capacitance cascode amplifier and a 50 Omega driver is reported. The receiver exhibited an improvement of factor of two in bandwidth over those using a conventional single inverter gain stage. An optical sensitivity of -27.5 dBm for an error rate of 10/sup -9/ at 1.3 mu m wavelength has been obtained without bandwidth equalisation or noise filtering.<>