PDC钻头切削齿布齿设计的新思路

切削齿布齿设计是PDC钻头设计的关键。为提高PDC钻头的钻进效率,综合考虑PDC钻头切削齿的设计特点和切削先后顺序等因素,并且通过对PDC钻头单切削齿实验结果进行分析,提出了以冠部轮廓法线为基准的切削齿布齿设计方法。     

Reliability of flip-chip bonded RFID die using anisotropic conductive paste hybrid material

A reliability of flip-chip bonded die as a function of anisotropic conductive paste (ACP) hybrid materials, bonding conditions, and antenna pattern materials was investigated during the assembly of radio frequency identification(RFID) inlay. The optimization condition for flip-chip bonding was determined from the behavior of bonding strength. Under the optimized condition, the shear strength for the antenna printed with paste-type Ag ink was larger than that for Cu antenna. Furthermore, an identification distance was varied from the antenna materials. Comparing with the Ag antenna pattern, the as-bonded die on Cu antenna showed a larger distance of identification. However, the long-term reliability of inlay using the Cu antenna was decreased significantly as a function of aging time at room temperature because of the bended shape of Cu antenna formed during the flip-chip bonding process.     

Effects of Cr interlayer on mechanical and tribological properties of Cr-Al-Si-N nanocomposite coating

Cr-Al-Si-N coatings were deposited on SUS 304 substrate by a hybrid coating system. A Cr interlayer was introduced between Cr-Al-Si-N coating and SUS 304 substrate to improve the coating adherence. The effects of Cr interlayer on the microhardness, adhesion, and tribological behavior of Cr-Al-Si-N coatings were systematically investigated. The results indicate that the microhardness of the Cr-Al-Si-N coatings gradually deceases with increasing thickness of Cr interlayers. The adhesion between Cr-Al-Si-N and SUS 304 substrate is improved by addition of the Cr interlayers. A peak critical load of ~50 N is observed for the coating containing Cr interlayer of 60 nm as compared ~ 20 N for the coating without Cr interlayer. The thicker Cr interlayers result in reduced critical load values. Moreover, the wear resistance of the Cr-Al-Si-N coatings is greatly enhanced by introducing the Cr interlayer with thickness of 60 nm in spite of the decreased microhardness. The friction coefficient of the coating system is also moderately reduced.     

有限负压下熔体硅中磷的挥发去除(英文)

对有限负压下熔体硅中磷的挥发去除进行研究。采用电子级硅配制Si-P合金,并采用GD-MS来检测实验前后硅中的磷含量。理论计算结果表明:在有限负压下,硅中的磷以P和P2的气体形式从熔体硅中挥发。实验结果显示:在温度1873K、真空度0.6-0.8Pa、熔炼3600s的条件下,熔体硅中的磷从0.046%(460ppmw)下降到0.001%(10ppmw)。实验结果与理论结果一致表明:当熔体硅中磷的含量大且炉腔内气压相对较高时,磷的去除与气压高度相关;而当炉腔气压很低时,磷的去除基本与气压无关。原因是在相对高磷含量的熔体硅中,磷主要以P2气体的形式挥发;在磷含量较低时,磷主要以单原子气体P的形式挥发。     

Enhancement of Voice Quality and Bit-rate Reduction by Prosodic Control in G.723.1 Vocoder

Speech coding techniques have been studied not only to reduce the complexity and bit rate but also to improve the sound quality.CELP type vocoder,used as standard,supports the great sound quality even low bit rate.In this paper,the preprocessing of input speech to reduce the bit rate is different from the conventional vocoder.Different kinds of parameter are used for the preprocessing compared with the other parameters to find the more appropriate parameter for the vocoder.The parameters are used to synthesize the speech not to encode or decode for coding technique so we proposed the simple algorithm not to have the influence on the processing time or the computation time.The parameters in the preprocessing step are speaking rate,duration,and PSOLA technique.     

纳/微异构型钙钛矿氧化物电极在固体氧化物燃料电池的研究进展

开发高效、稳定、廉价的钙钛矿氧化物电极材料是固体氧化物燃料电池(SOFC)进一步商业化发展的关键。目前,研究重点仍集中在解决阳极积碳、硫毒化以及阴极氧还原(ORR)低温性能不佳等问题。最近,有研究报道,一些易还原过渡金属元素掺杂的钙钛矿可以在还原气氛中原位析出该金属并以纳米颗粒的形式"镶嵌"在钙钛矿表面形成"纳米金属–钙钛矿"复合结构。该方法制备的材料具有性能高、抗积碳能力强、可再生性好等优点。从钙钛矿氧化物本体的选择、A/B位掺杂、缺陷调整、以及拓扑离子交换、相变诱发等方面,总结了近年来关于构建纳米(析出金属颗粒)微米(钙钛矿氧化物母体)异质结构(统称纳微异构)钙钛矿氧化物纳米纤维复合电极的研究。此外,总结了具有纳米纤维状形貌的钙钛矿氧化物电极及其结构对于SOFC性能、稳定性的影响,最后提出了该类纳微异构材料的优势、不足和展望。     

Surface properties of Al-doped ZnO thin film before and after CF4/Ar plasma etching

Al-doped ZnO (AZO) is considered as an alternative to transparent conductive oxide materials. Patterning and achieving a stable surface are important challenges in the development and optimization of dry etching processes, which must be overcome for the application of AZO in various devices. Therefore, in this study, the etch rate and surface properties of an AZO thin film after plasma etching using the adaptive coupled plasma system were investigated. The fastest etch rate was achieved with a CF₄/Ar ratio of 50:50 sccm. Regardless of the ratio of CF₄ to Ar, the transmittance of the film in the visible region exceeded 80%. X-ray photoelectron spectroscopy analysis of the AZO thin film confirmed that metal-F bonding persists on the surface after plasma etching. It was also shown that F eliminates O vacancies. Consequently, the work function and bandgap energy increased as the ratio of CF₄ increased. This study not only provides information on the effect of plasma on AZO thin film, but identifies the cause of changes in the device characteristics during device fabrication.     

Degradation Products of 2-tert-Butylhydroquinone at Frying Temperature

Decomposed products of 2-tert-butylhydroquinone (TBHQ) at frying temperature in model system were identified and characterized. An attempt was made to determine the functions of the decomposed compounds in foods using model system. Tert-butylbenzoquinone (TBBQ) was identified as the primary and major oxidation product of TBHQ. Interconversion between TBHQ and TBBQ was the most important role in antioxidant effectiveness and carry-through effect of TBHQ. Several types of dimers by ether linkage resulting from thermolysis at frying temperature were identified. In addition, significant reactivity of a phenolic antioxidant with the functional carboxyl group of a fatty acid, which might lower antioxidant effectiveness, was determined using a simple model system.     

D-Erythroascorbic Acid in Bakers'Yeast and Effects on Wheat Dough

Extraction of hydrated and freeze-dried bakers’yeast yielded ～ 50 μg erythroascorbic acid (EAA) and 5 μg ascorbic acid (AA)/g dry yeast as determined by HPLC with electrochemical detection. D-EAA (82 ppm based on flour) slightly increased the flow of dough as rest time increased. Gluten isolated from a flour-water dough containing 82 ppm D-EAA or 100 ppm Lcysteine stretched at a faster rate than control gluten. EAA like AA did not change dough development time. Unlike AA, EAA showed neither oxidizing effect on dough and gluten nor improving effects on bread.