Al-Ti-B-RE细化剂对Al-7．0Si-0．55Mg合金显微组织和力学性能的影响

研究添加Al-5Ti-lB-RE细化剂对Al-7．0Si-0．55Mg（A357）合金的显微组织和力学性能的影响。先利用真空熔炼技术制各Al-7．0Si-0．55Mg合金,然后在Al-7．0Si-0．55Mg合金中加入不同成分的Al-5Ti-1B-RE中间合金。通过X射线衍射仪（XRD）、金相显微镜（OM）和扫描电子显微镜（SEM）对显微组织和拉伸试样的断口形貌进行观察。在室温下对合金的力学性能进行测试。观察Al-5Ti-1B-RE细化剂的形态以及内部结构,可以发现以TiB,为异质形核核心的TiAl3／Ti2Al20RE的壳层结构相。在Al-7．0Si-0．55Mg合金中加入Al-5Ti-1B-3．0RE细化剂后,抗拉强度会有明显提升,直到0．2％添加量时,抗拉强度会达到峰值。     

Cellulose nanofibrils as templates for the design of poly(l-lactide)-nucleating surfaces

The abilities of surface-grafted cellulose nanofibrils for the nucleation of poly(l-lactide) (PLLA) were investigated. Cellulose nanofibrils with a width of ∼3 nm were obtained from wood cellulose via the oxidation using 2,2,6,6-tetramethylpiperidiniyl-1-oxyl as a catalyst and successive mechanical treatment. The cellulose nanofibril surfaces were selectively modified with amine-terminated poly(ethylene glycol) chains, via simple ionic bonds. The PEG-grafted cellulose nanofibril/PLLA composite films were prepared using a solvent casting method with chloroform. The isothermal and non-isothermal crystallization kinetics of the PLLA in the composites was studied using differential scanning calorimetry and polarized optical microscopy. The PEG chains were densely immobilized on the surface of the cellulose nanofibril templates, which had extraordinarily large specific surface areas. As a result, the surface-PEG layers effectively increased the rate of crystallization of the PLLA in the composites. Because of the increased degree of crystallinity after the isothermal crystallization, the composites showed better heat resistance than neat PLLA.     

Mixture distribution measurement using laser induced breakdown spectroscopy in hydrogen direct injection stratified charge

Reduction in cooling loss due to the heat transfer from burning gas to the combustion chamber wall is very important for improving the thermal efficiency in hydrogen engines. The previous research has shown that the direct injection stratified charge can be a technique to reduce the cooling loss and improve thermal efficiency in hydrogen combustion. For effective reductions in cooling loss by the stratified charge, it is very important to know the relation between the fuel injection conditions and mixture distribution. The current research employs the laser induced breakdown spectroscopy as a method to measure the hydrogen concentration distribution in the direct injection stratified charge. Measurement of instantaneous local equivalence ratio by the method clears the characteristics of mixture formation in hydrogen direct injection stratified charge. This research also tries to actively control the mixture distribution using a split fuel injection.     

Composition dependence of young’s modulus in Ti-V, Ti-Nb, and Ti-V-Sn alloys

The Young’s modulus of Ti-V and Ti-V-Sn alloys quenched from the β-phase region after solution treatment and cold rolling was investigated in relation to alloy compositions, microstructures, and constituent phases. The composition dependence of the Young’s modulus for quenched Ti-V binary alloys shows two minima of 69 GPa at Ti-10 mass pct V and 72 GPa at Ti-26 mass pct V. Between the two compositions, athermalω or stress-induced ω is introduced in retainedβ phase and increases Young’s modulus. That is, a low Young’s modulus is attained unless alloys undergoω transformation. In Ti-5 and -8 mass pct V, which under goα′ (hcp) martensitic transformation on quenching, the Young’s modulus further decreases by cold rolling, which can be reasonably explained by the formation ofα′ rolling texture. Comparing Young’s modulus in Ti-V binary alloy with that in Ti-Nb binary alloy, it is found that Young’s modulus is remarkably increased by athermal- or stress inducedω phase, and it shows a minimum when both martensitic andω transformation are suppressed during quenching in metastableβ alloys. The Sn addition to Ti-V binary alloy retards or suppresses athermal and stress-inducedω transformation, thereby decreasing Young’s modulus. Young’s modulus exhibits minimum values of 51 GPa in quenched (Ti-12 pct V)-2 pct Sn and of 57 GPa in cold-rolled (Ti-12 pct V)-6 pct Sn.     

用倒锥形测头测量蜗杆及滚刀齿形的测头半径补偿

根据倒锥形测头中心的轨迹曲线,分析了测量接触点与测头中心的相对位置关系。提出消除由于测头半径所引起的测量误差的原理,并给出了圆弧齿轮滚刀的齿形测量实例。     

Analog Circuit Design Methodology in a Low Power RISC Microprocessor

There are various kinds of analog CMOS circuits in microprocessors. IOs, clock distribution circuits including PLL, memories are the main analog circuits. The circuit techniques to achieve low power dissipation combined with high performance in newest prototype chip in the Super H RISC engines are described. A TLB delay can be decreased by using a CAM with a differential amplifier to generate the match signal. The accelerator circuit also helps to speed up the TLB circuit, enabling single-cycle operation. A fabricated 96-mm² test chip with the super H architecture using 0.35-m four metal CMOS technology is capable of 167-MHz operation at 300 Dhrystone MIPS with 2.0-W power dissipation.     

Preparation of porous sheet composite impregnated with TiO<Subscript>2</Subscript> photocatalyst by a papermaking technique

Titanium dioxide (TiO₂) powder-containing sheet composites, called TiO₂ sheet, were prepared by a papermaking technique, and their photocatalytic efficiency was investigated. The TiO₂ powders were homogeneously scattered over the fiber-mix networks tailored within the catalyst sheet. Under UV irradiation, the TiO₂ paper could decompose p-hydroxyacetophenone (p-HAP), although the degradation efficiency by the TiO₂ sheet was lower than that by the TiO₂ powder. Scanning electron microscopy revealed that coverage of the TiO₂ particles inside the sheet by alumina binder which was used to improve the sheet strength caused the deterioration of the photocatalytic performance. Internal addition of alumina binder made the TiO₂ sheet porous and such a TiO₂ sheet exhibited high photocatalytic performance equivalent to that of TiO₂ powder. The porous structure of TiO₂ sheet might contribute to effective transport of p-HAP to the surface of TiO₂ particles inside the sheet, resulting in high degradation performance. In addition, TiO₂ sheet prepared using TiO₂ sol showed higher photocatalytic efficiency than TiO₂ powder and it was indicated that the porous sheet structure might provide suitable conditions for TiO₂ catalysis for photodecomposition.     

2-甲基-8-（9，9-二丁基芴）-3，5，7-三炔-2-辛醇的合成和性质研究

合成了一种新颖的乙炔衍生物，2-甲基-8-（9，9-二丁基芴）-3，5，7-三炔-2-辛醇（6a），并利用红外光谱（IR），紫外光谱（Uv），核磁（NMR），质谱（MS）等对其结构进行了表征。利用红外光谱（IR）和紫外光谱（Uv）对其拓扑固相聚合性质进行了研究。实验结果表明，这些化合物在加热和紫外光照射条件下都能够发生固相聚合，但得到的是结构复杂的聚合物。     

Growth of emerald crystals from PbO · V2O5 flux

The flux growth of emerald crystals by slow cooling in the PbO · V₂O₅ flux is reported. The crystals exhibited the typical emerald-green colour, were up to 1.8 mm in size and transparent. Their form was a regular hexagonal rod bounded by the well-developed {0001} and {10ˉ10} faces. The solubility of emerald in PbO · V₂O₅ was also investigated; about 9.0 g emerald was dissolved in 100 g PbO · V₂O₅ at 1200 °C. The solubility decreased gradually with decreasing temperature. Taking the solubility data into account, the presence of undissolved particles in the solution was found to be a necessary condition for the growth of large emerald crystals. Unsaturated solution at a soak temperature produced good and relatively small emerald crystals in a subsequent cooling experiment. Advantages of the PbO · V₂O₅ flux are also mentioned. Emerald crystals showing various kinds of imperfections, and even good crystals, were also present.