小浪底水库坝前漏斗区泥沙测验分析

小浪底水库坝前漏斗区的形成和发展,直接影响到枢纽建筑物的安全运行。为了保持塔前“门前清,”掌握坝前漏斗区的形成和发展,保证水库进入拦沙后期和正常运用期的正常运用,对坝前漏斗区进行了泥沙测验分析。结果表明:目前漏斗区范围内纵向坡度较缓,尚没有明显的漏斗形成,仅在坝前和塔前200m×1000m范围形成了漏斗雏形。     

Nickel- and copper-coated carbon fibre reinforced tin-lead alloy composites

Nickel and copper were deposited over brominated, surface treated, and pristine P-100 carbon fibres using cementation and electroplating techniques. The fibres were brominated by bromine vapour for 48 h and then desorbed at 200 °C in air for 12 h. The anodic oxidation treatment of the fibres involved electrochemical etching in a dilute sodium hydroxide electrolyte for 3 min. Electroplated coated fibres showed better tensile properties than cementation coated fibres. In addition, nickel coating exhibited better bonding with the carbon fibres compared to copper coating. The effect of bromination and surface treatment was improved adhesion between coating and fibres. Nickel- and copper-coated fibres, which were brominated, anodically oxidized, and pristine, reinforced tin-lead alloy composites were fabricated by squeeze casting. The composites containing coated treated carbon fibres had higher tensile and shear strength than the ones containing coated pristine carbon fibres. Moreover, the composite with coated brominated carbon fibres had better tensile strength and shear strength than the surface treatment. The results also showed the composites containing nickel-coated fibres had higher tensile and shear strength than the ones containing copper-coated fibres.     

Long fiber reinforced polyamide and polycarbonate composites. II: Fatigue behavior and morphological property

Fatigue behavior and morphology of long glass fiber reinforced semicrystalline polyamide (nylon 6,6) and amorphous polycarbonate (PC) composites were investigated. The fiber length distribution in the molded samples was calculated by image analyzer. The tension-tension fatigue loading tests at various levels of stress amplitudes were studied. The two-parameter Weibull distribution function were applied to obtain the statistical probability distribution of experimental data. A good correlation existed between the experimental data and the Weibull distribution curves. Straight line S? N curves of long glass fiber reinforced semicrystalline polyamide and amorphous polycarbonate composites at various probabilities were established. The stiffness of the composite under tension-tension fatigue loading was measured. The thermal stress history was also investigated by thermo-imaging techniques during fatigue life testing. Further, failure morphology was examined by scanning electron microscopy (SEM). The results showed that the fracture behavior of the ductile damage in polyamide is different from the brittle damage in polycarbonate.     

重力坝深(底)孔断面钢筋混凝土模型试验研究

文通过7个小尺寸和1个大尺寸的钢筋混凝土断面模型试验，研究重力坝深(底)孔在坝体自重和内水压力以及超内水压力作用下的结构特性和破坏规律。重点探讨混凝土和钢筋应力应变、混凝土开裂、裂缝宽度和裂缝扩展规律，为建立更为科学的孔口配筋理论提供依据。     

Delayed delivery of surviving triplet after fetal reduction and spontaneous abortion

In multiple pregnancies, survival of remaining fetuses after premature death and delivery of one fetus is uncommon. We report a case of a triplet pregnancy that was reduced to twins at the 14th gestational week and then had preterm premature rupture of membranes and intrauterine fetal death of one twin at the 17th gestational week. To save the surviving fetus, delivery of the dead fetus and ligation of the umbilical cord at the cervical level were performed. We also performed McDonald cervical cerclage to keep the placenta of the dead fetus as well as that of the surviving one in the uterine cavity. After a series of aggressive procedures, including immediate administration of tocolytic agents, and antibiotic prophylaxis to prevent infection and preterm labor, the surviving fetus was delivered vaginally 73 days later due to intractable uterine contractions. After a 10-week hospital stay, the infant boy, weighing 2,500 g, was discharged without any sequelae. To our knowledge, this was the longest interval between deliveries in a triplet pregnancy reported in Taiwan. With adequate intensive management, a satisfactory outcome of the fetus and mother in such cases is possible.     

Ultra-shallow p-junction formation in silicon by excimer laser doping: a heat and mass transfer perspective

Heat and mass transfer at the nanosecond time scale and the nanometer length scale in pulsed laser fabrication of ultra-shallow p⁺-junctions is studied in this work. A new technique is developed to fabricate the ultra-shallow p⁺-junctions with pulsed laser doping of crystalline silicon with a solid spin-on-glass (SOG) dopant, through the nanosecond pulsed laser heating, melting, and boron mass diffusion in the 100 nm thin silicon layer close to the surface. High boron concentration of 10²⁰ atoms cc⁻¹ and the ‘box-like’ junction profile are achieved. The key mechanism determining the ‘box-like’ junction shape is found to be the melt-solid interface limited diffusion. The ultra-shallow p⁺-junctions with the depth from 30 to 400 nm are successfully made by the excimer laser. The optimal laser fluence condition for SOG doping is found about 0.6–0.8 J cm⁻² by studying the ultra-shallow p⁺-junction boron profiles measured by the secondary ion mass spectroscopy (SIMS) vs the laser fluence and the pulse number. The one-dimensional numerical analysis agrees reasonably with the experiment, within the available physical picture. Possible mechanisms such as boron diffusivity dependence on the dopant concentration in the molten silicon are proposed.     

Exceptional convergent evolution in a virus

Replicate lineages of the bacteriophage phiX 174 adapted to growth at high temperature on either of two hosts exhibited high rates of identical, independent substitutions. Typically, a dozen or more substitutions accumulated in the 5.4-kilobase genome during propagation. Across the entire data set of nine lineages, 119 independent substitutions occurred at 68 nucleotide sites. Over half of these substitutions, accounting for one third of the sites, were identical with substitutions in other lineages. Some convergent substitutions were specific to the host used for phage propagation, but others occurred across both hosts. Continued adaptation of an evolved phage at high temperature, but on the other host, led to additional changes that included reversions of previous substitutions. Phylogenetic reconstruction using the complete genome sequence not only failed to recover the correct evolutionary history because of these convergent changes, but the true history was rejected as being a significantly inferior fit to the data. Replicate lineages subjected to similar environmental challenges showed similar rates of substitution and similar rates of fitness improvement across corresponding times of adaptation. Substitution rates and fitness improvements were higher during the initial period of adaptation than during a later period, except when the host was changed.