Advanced Materials Research Vol. 216

Abstract: Efficient ~1.48 and ~1.8mm infrared emissions have been recorded in Tm³⁺ doped mixed alkali/alkaline-earth modified heavy-metal gallate glasses (LKBPBG) with low phonon energy under 793nm excitation. Judd-Ofelt parameters W₂ (4.34´10^-20cm2), W₄ (9.74´10^-21cm2) and W₆ (1.00´10^-20cm2) indicate a higher asymmetric and stronger covalent environment in the glass material. The spontaneous transition probability and maximum emission cross-section of ³H₄→³F₄ transition are derived to be 283s^-1 and 2.90´10^-21cm2. The maximum emission cross-section of ³F₄→³H₆ transition is calculated to be 6.82´10^-21cm2, and the ideal net gain coefficients at 1.675 (U-band edge) and 1.872mm are given to be 0.56 and 3.51dB/cm, respectively, as the population inversion equals 1.0, which provide a theoretical anticipation in developing U-band amplifiers and eye-safe medical lasers.

Abstract: A novel visual detection set, which can detect sub-superficial defects in conductive specimens, is presented in this paper. The set has a laser source, a charge coupled device (CCD) camera, and a magnetic excitation. The linear polarized light given off by the laser source is modulated by the superimposition of the magnetic fields induced by the coil and eddy current, and acquired by the CCD. Given the exciting current is known and the eddy current is influenced by the defects, the information of defects can be extracted from the image acquired by CCD. The magnet excitation and image processing are described in detail. Experimental tests have been done and the method presented is proved by the experimental results.

Abstract: This paper discussed the working principle, classification, modeling process and technology features for rapid tooling based on rapid prototyping and investigated into the difference between rapid tooling with traditional modeling manufacture. Several typical rapid tooling technologies are compared and summarized from mould period, fabrication cost and production cycle. Some key problems that rapid tooling industry will face with are analyzed. The application of the rapid tooling based on rapid prototyping is prospected.

Abstract: Optical code division multiple access (OCDMA) passive optical network (PON) can find wide applications in the next optical access network. One of its key techniques of is construction of address code. Aiming at the facts that (F,K,1) optical orthogonal code (OOC) possesses good performance but capacity is small, and number of users in OCDMA PON is not very big thereafter OOC auto-correlation or cross-correlation may not be very strict, (F,K,2) OOC can be used as address codes for OCDMA PON. In this paper, the method of constructing OOC based on block design is discussed. The algorithm of construction (F,K,2) of OOC from block design is presented and simulated; several groups of (F,K,2) OOC are gained. The results show that the algorithm has good astringency and simplicity. It can construct (F,K,2) OOC effectively. It is feasible.

Abstract: Designing a top-stem-cutter part for the top-cutter machine. Adams was used to analysis the moving simulation, with the help of it, the normal structure and dimension were inspected and verified. In this paper, the tract of the top-stem-cutter part analyzed by Adams was matched the result from the theoretical calculations; the model and structure also had been analyzed by Ansys, which provided a way to analysis and verify the machine, and analysis of the model can get the nature frequency of the top-stem-cutter part, and it had given us a way to lower frequency of machine; the structure analysis provided that the stress of the top-stem-cutter part should be lower than certain value.

Abstract: Producing in the multiprogramming systems of the demanding paging style ,thrashing is an extreme status coming from doing page replacement. Based on some research results, the cause of thrashing is discussed with describing the feature of it. A policy of "preventing first" is presented to hold on to refrain from the thrashing ,which sets forth the concrete method of preventing and ending the thrashing. Some relating conclusions are also fit for page replacements of the computer designing in other fields.