短纤维增强透气性莫来石/铁(A3S2/Fe)复合材料烧结特性的研究

本文研究了A₃S₂/Fe复合材料的烧结特性、透气性和纤维增强效果,分析了烧结过程中材料宏观结构和微观组织的形成机理.实验结果表明:纤维增强A₃S₂/Fe复合材料在900～1000℃具有良好的烧结性能,烧成后表层存在一定厚度的硬化层;纤维增强效果显着.材料抗压强度达17～23MPa,相对透气系数为4.30～9.69cm3/(cm2·s·atm).已能满足实际应用的需要.     

Comments on “Multiphase systolic algorithms for spectraldecomposition” [and reply]

Comments that the paper by Liu and Yao (see ibid., vol.40, no.1, p.190, 1992) presented an efficient algorithm for spectral decomposition, but the parallel algorithm and architecture for the Hessenberg reduction has a problem. The matrix obtained from the unitary similarity transformation is not necessarily a Hessenberg matrix. The authors reply that the Hessenberg reduction described is not in the Hessenberg form. Only the first column is in its proper form. There are many ways to overcome such a problem. One simple way is to use the multiphase rectangular systolic array     

MX345芯片及单片机控制

MX345芯片用于产生模拟信令—CTCSS单音.本文在介绍MX345编码/解码器工作原理的基础上,设计出MX345芯片与单片机的接口电路.最后给出控制软件.     

Comparison of demineralized allogeneic bone matrix grafting (the Urist procedure) and the Ilizarov procedure in large diaphyseal defects in sheep

The bone inductive capability of the Urist and Ilizarov procedures was compared in the repair of large diaphyseal defects in sheep. In 30 animals, a 4 cm segmental defect was created in the middle portion of the right femur and was stabilized with an external fixator. The sheep were divided into four groups according to the type of reconstruction of the defect. In group 1, a demineralized allogeneic bone matrix (DABM) cylinder was used; in group 2, DABM chips; and in group 3, gradual transport of a piece of bone detached from the proximal femoral fragment was used to fill the defect. Group 4 served as a control (the defect was left empty). New bone formation was assessed by serial radiographs until the time of death at 2 or 4 months. Postmortem specimens were analyzed with respect to bone mineral content, uptake of isotopes (45Ca and 3H-proline), and histology. The first signs of new bone formation were radiographically evident at 4 weeks. In the two groups in which reconstruction involved DABM (Urist procedures), new bone failed to form in eight of the 13 animals. Full bridging of the defect was observed at 8 weeks in one animal with a DABM cylinder and two with DABM chips. No decisive difference in bone yield could be demonstrated between the two Urist procedures. In the group treated with the Ilizarov procedure, new bone formation consistently occurred at a high rate; full bridging of the defect was observed in seven of the eight animals. Bone mineral scanning and histologic analysis essentially confirmed the radiographic results. Uptake of isotopes was selectively analyzed in two sheep from each experimental group in which new bone formation was exhibited in the defect; new bone formation was increased compared with that in the contralateral femur but was equal among the three experimental groups. Our study shows that gradual transport of a detached piece of autogeneic bone (Ilizarov procedure) is more effective than implantation of DABM (Urist procedure) in eliciting new bone formation in large diaphyseal defects in sheep. The variable bone induction by DABM may be explained by differences in host immune responses to the implants.     

Magnetic resonance findings in skeletal muscle tears

Magnetic resonance (MR) images of skeletal muscle tears can clearly delineate the severity of muscle injury. Although MR imaging is seldom necessary in patients with acute muscle trauma, it can be helpful in deciding on clinical management. The two major MR findings in acute muscle tears are deformity of the muscle and the presence of abnormal signal reflecting hemorrhage and edema. In acute tears, methemoglobin within the extravascular blood causes high-signal areas on both T1- and T2-weighted images. With partial tears, the blood may dissect in a distinctive linear pattern along the muscle bundles and fibers. As healing begins, the muscle signal diminishes, first on the T1-weighted images and then on the T2-weighted images. When there is residual abnormal signal on images obtained more than several months after the injury, it is presumed to represent hemorrhage from recurrent tears. In patients with a questionable history of a remote injury, the clinical presentation may be that of persistent pain or a soft tissue mass. In these cases MR imaging may identify the cause of the pain and can exclude a neoplasm by proving that the mass is a hypertrophied or retracted muscle. Thus, MR imaging has a limited, but occasionally important role in selected patients with skeletal muscle tears.     

广义Hénon系统的广义超混沌同步

提出实现广义混沌或超混沌同步的一种构造响应系统的方法.该方法从已知的混沌或超混沌驱动系统出发,拆分并保留系统稳定的线性部分,通过对驱动系统变量的线性变换构造出响应系统.以具有超混沌特性的广义H啨non离散系统为例,理论分析和数值计算的结果完全一致,表明该方法对于构造广义混沌和超混沌同步系统十分有效.     

Effects of irradiation in combination with waxing on the essential oils in orange peel

The study evaluated the effects of waxing, irradiation dose and post‐irradiation storage time on the essential oils in orange peel. Mature oranges (Maroc late) waxed or unwaxed were treated with 1 or 2 kGy radiation and stored for 9 weeks at 20 °C and 40–50% RH. Essential oils from the peel were extracted and analysed by GC. Results showed that D ‐limonene was significantly lower in waxed oranges; levels in samples treated with 2 kGy were higher than those in non‐irradiated or treated with 1 kGy. Linalool, methyl anthranilate and 3,7‐dimethyl‐2,6‐octadienal decreased as the dose increased. Levels of linalool increased with storage time but D ‐limonene was unaffected. These results may aid in guaranteeing the quality of orange essential oils during storage time. Copyright © 2004 Society of Chemical Industry