Axisymmetric dynamic response of a penny-shaped crack to a pair of transient concentrated forces

The three-dimensional axisymmetric elastodynamic response of a penny-shaped crack embedded in an infinite elastic solid subjected to a pair of transient concentrated forces is investigated. The forces are applied on the symmetry axis perpendicular and symmetric to the crack surfaces, including the special case when the forces act precisely on the crack surfaces. A time-domain boundary integral equation method is applied for computing the crack-opening displacement and subsequently the time dependence of the dynamic stress intensity factors. Numerical calculations are carried out for various geometry parameters and the results are discussed. It is found that the location of the applied concentrated forces inducing the highest dynamic stress intensity factors differs from that producing the highest static values.     

Iron requirements and iron balance during pregnancy. Is iron supplementation needed for pregnant women?

Among fertile, nonpregnant, Danish women, 33% have absent or reduced iron stores; 22% have serum ferritin values above 70 micrograms/l, i.e., iron reserves of more than 530 mg, corresponding to the net iron losses during a normal pregnancy. During pregnancy, the demands for absorbed iron increase from 0.8 to 7.5 mg/day. Controlled studies show that iron-treated pregnant women have higher serum ferritin levels, i.e., larger iron stores, and higher haemoglobin levels than placebo-treated women. A supplement of 66 mg ferrous iron daily from the beginning of the 2nd trimester prevents iron deficiency anaemia. In Denmark, general iron prophylaxis with 60-70 mg ferrous iron daily from 20 weeks of gestation is recommended by the health authorities.     

Multimedia Signal Processors: An Architectural Platform with Algorithmic Compilation

Novel algorithmic features of multimedia applications and advances in VLSI technologies are driving forces behind the new multimedia signal processors. We propose an architecture platform which could provide high performance and flexibility, and would require less external I/O and memory access. It is comprised of array processors to be used as the hardware accelerator and RISC cores to be used as the basis of the programmable processor. It is a hierarchical and scalable architecture style which facilitates the hardware-software codesign of multimedia signal processing circuits and systems. While some control-intensive functions can be implemented using programmable CPUs, other computation-intensive functions can rely on hardware accelerators.To compile multimedia algorithms, we also present an operation placement and scheduling scheme suitable for the proposed architectural platform. Our scheme addresses data reusability and exploits local communication in order to avoid the memory/communication bandwidth bottleneck, which leads to faster program execution. Our method shows a promising performance: a linear speed-up of 16 times can be achieved for the block-matching motion estimation algorithm and the true motion tracking algorithm, which have formed many multimedia applications (e.g., MPEG-2 and MPEG-4).     

Sizing and characterization of ultrasonic indications using imaging techniques

For discontinuity analysis more and more sophisticated methods are used in the nuclear industry. The rapid development of computer technology offers the possibility to use imaging techniques. Instead of specialized focusing transducers the more flexible synthetic focusing techniques can be used. Presupposing that the material is ultrasonically isotropic and homogeneous, imaging techniques make it possible to visualize the reflectivity of the volume to be tested.Siemens developed the high speed holographic instrument Holo 3000 in cooperation with the University of Bochum. In this paper the method of Broad Band Holography is presented in the context of other imaging techniques.Different filtering methods have been investigated in order to achieve highest resolution and best signal to noise ratio with a given dataset. Different transducers respective wave modes have been applied to austenitic welds and claddings. The reconstructed image was evaluated using image processing techniques in order to investigate the possibilities to produce results easier to be quantifed than the original reconstruction.The results presented show a reliable expert tool for analysis measurements which also can be used for flaw detection.     

Silver dissolution on copper-based alloys

Electrical resistivity measurements and scanning electron microscopy was used to study the dissolution of silver on Cu-Ag and Cu-Al-Ag alloys. The results seem to indicate that the dissolution temperature is affected by the addition of aluminium.     

几何设计约束的表示与满足问题研究

对于智能ＣＡＤ系统来说，具有解决几何设计约束的功能是重要的。本文提出了一种面向对象的几何设计约束表示方法，它可以通过两种方式来表达。文中给出了一个约束传播算法，用于解决约束满足问题。