WAVE INTERACTION WITH PERFORATED CAISSON BREAKWATERS

The reflection coefficient of perforated caissons and the total horizontal forces acting on them were experimentally and numerically analyzed and discussed when wave propagates normally. To consider the viscosity effect of fluid and nonlinear action of waves on structures, the VOF (Volume Of Fluid) method combined with the k-ε turbulence model was used to simulate the interaction between waves and structures. Governing equations were solved with the finite difference method. Through 2D experimental study in the wave flume, the empirical relationship between the reflection coefficient of perforated caissons and the main affecting factors were obtained from the experimental data using the least square method. Also the correlation between the ratio of the total horizontal force acting on perforated caisson and the force acting on solid caisson and the main affecting factors were regressed from the experimental data.     

Failure analysis of a broken tooth

Several days after heart surgery, a patient discovered his upper right canine tooth had broken at the root. Such tooth damage, recognized post-operatively, is usually assumed to be caused by blunt mechanical force from an instrument used by the anesthesiologist during placement of a breathing tube at the start of surgery. In this case, the patient had saved the crown portion of the broken tooth, and it was possible to examine the root fracture characteristics. The curvature and direction of the crack path and natural tooth situation suggested that failure could be described through a cantilever beam model. This was confirmed when a whole extracted sample tooth was embedded and broken by a measured force in a manner consistent with the model. The resulting fracture surface matched that of the patient’s broken canine tooth. However, the high load and force direction necessary to fracture the root was inconsistent with forces applied during the anesthesia procedure. The failure analysis and further investigation indicated tooth clenching on the breathing tube during recovery was the likely cause of fracture. This paper presents an alternate explanation for intubation-related dental injury, demonstrates the practicality of fractographic analysis of biological materials, and introduces a methodology for simulating in vitro tooth settings for mechanical testing.     

600 A IGBT开关电路及其散热系统设计

采用IGBT开关电路，对大功率电阻带进行直流脉宽调制控制，实现了内燃机车大功率直流发电机负载实验中的负载大小的连续调节。为了避免在实验过程中IGBT器件的温度过高，采用独特的双管IGBT结构和双向强迫风冷的散热系统。实验表明该电路运行稳定、可靠。     

摩擦强度对薄膜表面形态的作用:原子力显微镜下的观察

展示了摩擦强度对聚酰亚胺薄膜表面形态的影响，原子力显微图像显示，机械摩擦会使聚酰亚胺薄膜表面上形成微沟槽，这些沟槽的表面具有丰富的表面精细构造。原子显微图像还揭示了机械摩擦可以改变被磨擦聚酰亚胺膜的表面形态。     

电算法在液压支架受力分析中的应用

建立支架受力分析的电算设计数学模型并给出程序框图     

Discrimination of B–C–N nanotubes through energy-filtering electron microscopy

Various multi-walled nanotubes in the B–C–N system are thoroughly investigated using a JEOL-3100FEF high-resolution field emission transmission electron microscope operating at 300 kV and equipped with an in-column built Omega filter. Spatially-resolved B, C and N elemental maps of the nanotubes are constructed. It is realized that a wide variety of tubular arrays composed of B, C and N atoms may exist in the system. Sandwich-like BN-rich and C-rich alternating tubular shells, graphitic C layers inside and outside of pure BN shells induced either by surface contamination, or electron beam irradiation, separation of C-rich and BN-rich tubes and/or BN particles within tubular bunches may take place. One should carefully take these effects into account while analyzing nanotube physical properties, e.g., electrical or optical, rather than simply rely on electron energy loss spectra typically collected from B, C and N containing nanostructures as a whole. Striking dependence of an individual nanotube electrical conductivity on tubular shell chemistry is demonstrated using I–V curve recording in an atomic force microscope.     

Removal of As(V) Ions from Solution by Akaganeite bgr-FeO(OH) Nanocrystals

The original method is developed for producing the new inorganic sorption material of akaganeite bgr-FeO(OH). The material in question is characterized relative to arsenic contained in aqua. The possibility is established for removing arsenate ions from water by contemporary physicochemical methods.     

Nucleation of branches in elastomeric polypropylene

The formation of a crosshatched morphology during crystallization of an isotactic polypropylene with low crystallinity is studied in detail. Here, a lamella seems to grow through another nearly perpendicular lamella that was crystallized before. The crystallization was observed with in situ scanning force microscopy with a temporal resolution of 3 min per image. After crystallization the volume structure was imaged by nanotomography. A detailed scheme for the nucleation of branches is proposed.     

Highly oriented star-like patterns observed on GaSe epilayers grown on Si(111)

Epitaxial lamellar gallium selenide (GaSe) semiconductors have been grown on trench-patterned silicon (Si) substrates by molecular beam epitaxy. An intriguing star-like patterned morphology was identified by atomic force microscopy on these epilayers. This non-trivial feature can be correlated with the accumulation of stacking faults of two concurrent epitaxial domains around self-oriented triangular pits developed earlier on the Si(111) surface by the chemical etching. Crystallographic considerations show how the stars can be formed.     

Synthesis of selenium nanoparticles in the presence of silk fibroin

This paper describes a solution-phase approach to the synthesis of selenium nanoparticles by reducing selenious acid solution with ascorbic acid in the presence of silk fibroin. The monodispersed spherical selenium colloid particles obtained were very stable in silk fibroin solution and characterized by Atomic force microscopy and X-ray techniques. The influences of temperature and ultrasonication on the morphology of selenium nanoparticles were also discussed. The experiments showed that the selenium nanoparticles with various morphologies could be obtained under different temperatures and the appropriate ultrasonication time was 60 min. This result indicated that the silk fibroin molecules intimately associated with the surface of the selenium particles and controlled the growth particles.