Scattering of plane SH-waves by a cylindrical canyon of arbitrary shape in anisotropic media

The scattering and diffraction of plane SH-waves, by an arbitrary-shaped cylindrical canyon in anisotropic media is formulated here. Analytical solutions are obtained via the complex function theory, using the orthogonal property of the Hermite functions to solve the resulting set of infinite algebraic equations. Expressions for scattered displacements and scattered stresses are given. Three cross-sectional profile types are used in the numerical simulation of the two-dimensional canyon topography: (a) a semi-circular profile, (b) a semi-elliptical profile and (c) a triangular profile. The results obtained in (a) and (b) are consistent with known solutions computed by Trifunac and his co-workers [1,3] using a different method. As the exact solution for (c) is not known to exist, the result given here is believed to be new and would therefore serve as a useful check for numerical analysts working in this area.     

高性价比DSP驰骋消费类电子器件市场

性价比几乎在所有产品中都举足轻重,其重要性在消费类电子产品中更是发挥到了极至。在这些产品中,设计工程师在实现关键性能要求的同时,还要尽力降低成本。对更高性能、更低价格的不断追求现在已开始束缚DSP制造商的手脚。当然,从总体来看,电子元件仍在继续提供更高的性价比,但有时在事实上存在着某种无形的心理界限。一旦某个元件突破了这种界限,马上会有众多应用对其趋之若骛,而其中某些应用是芯片厂商们从未料到的。对高性能 DSP 来说,其中一个界限是500 元人民币。事实上某些中等性能的 DSP 能够达到这个价格,但是电子业仍在致力于…     

Out-of-plane vibrations of thick rings

Natural out-of-plane vibrations of thick circular rings are considered using an accurate shear deformable theory of which the classical and the Timoshenko-type shear deformation theory are special cases. The present formulation uses no shear correction factors since the assumed shear strain variations are nonlinear across the cross-section. The numerical results presented illustrate the accuracy of the present formulation.     

Factors affecting the use of folic acid supplements in pregnant women in Glasgow

BACKGROUND: Use of folic acid supplements preconception, and during the first trimester, is associated with a reduced incidence of first and subsequent neural tube defects. The Department of Health guidelines recommend the use of folic acid supplements by all women planning a pregnancy. AIM: To ascertain the proportion using folic acid supplements and the factors affecting their use. METHOD: Questionnaires were distributed postpartum to the 515 women who delivered normal babies in three maternity units in Glasgow over a four-week period. RESULTS: Forms were completed by 487 (95%) women. Only 57% took supplements at some point during their pregnancy, and only 21% took them before conception. Failure to take supplements was significantly associated with unplanned pregnancy, younger age, and previous pregnancies. Lack of awareness of the potential benefits associated with folic acid use was the commonest reason cited by women for not taking supplements. CONCLUSIONS: Increased health education through health care professionals and mass media campaigns can improve awareness and thereby increase the use of supplements in planned pregnancies. However, 42% of women in our study had unplanned pregnancies. Intake of folic acid supplements in this group can only be increased by improvements in dietary intake within the population as a whole, and by fortification of commonly ingested foods.     

Fault diagnosis under a limited-fault assumption and limited test-point availability

This paper describes a method of fault diagnosis for large interconnected circuits in which the number of faults is limited to, say,n _f where it is possible thatn _f exceeds the number of output measurements,n _o. The problem and its solution are formulated in the context of a frequency domain tableau based on the component connection model of a circuit/system. The paper describes Jacobian tests for diagnosability whenn _fn _o and states a full parameter diagnosability test as a corollary to the main theorem. An algorithm is developed for the identification of faulty parameters in this limited fault case. Finally, examples, including a 26-parameter video-amplifier circuit, illustrating the technique are given.     

Thermodynamics of the Na2O−P2O5 system

The activity of Na₂O in the melts of the Na₂O?P₂O₅ system has been determined using a high temperature electrochemical cell with a Na₂O?WO₃ melt at the reference electrode and fused silica as the solid electrolyte as shown below. $$_{Na_2 O - WO_3 melt}^{Pt(s),O_2 (g)} \left| {_{fused silica}^{ Na^ + } } \right|_{Na_2 O - P_2 O_5 melt}^{O_2 (g), Pt(s)} $$ The thermodynamics of the Na₂O?P₂O₅ binary system in the composition range of 50 to 75 mole pet Na₂O has been studied. The activities of Na₂O and P₂O₅ in the melt have been carefully analyzed. The free energy of four sodium phosphates has been evaluated with the help of the phase diagram of this system. Based on this study, a solid-state phase transformation for the 3Na₂O·P₂O₅ compound has been suggested at a temperature below 1217 K. The entropy of the transformation is near zero. The enthalpy of transformation is estimated to be 101.51 kJ/mole 3Na₂O·P₂O₅.