GCr15钢旋转弯曲超长寿命疲劳性能分析

轴承钢GCr15旋转弯曲超长寿命疲劳实验获得的应力-寿命(S-N)曲线数据分散性较大且呈连续下降趋势,不能用台阶下降的S-N曲线描述.断口分析表明,在高应力幅区疲劳破坏主要起始于试样表面的加工划痕或夹杂物;随着应力幅的降低,疲劳破坏主要起始于试样内部的夹杂物.内部破坏均带有鱼眼特征,大部分的内部夹杂物周围带有颗粒亮区(GBF区).夹杂物尺寸的较大分散程度和小尺寸夹杂物的簇集是引起GCr15钢疲劳寿命分散性较大的因素.使用推定的GBF区成长率能够定量分析夹杂物尺寸对疲劳寿命分散程度的影响.     

Electrical and thermal conductivities of porous SiC/SiO2/C composites with different morphology from carbonized wood

Porous SiC/SiO₂/C composites exhibiting a wide range of high thermal and electrical conductivities were developed from carbonized wood infiltrated with SiO₂. As a pre-treatment, the samples were either heated at 100 °C or kept at room temperature followed by sintering in the temperature range 1200–1800 °C. The microstructure, the morphology, and the electrical and thermal conductivities of the composites were investigated. Pre-treatment at room temperature followed by sintering up to 1800 °C produced composites exhibiting a greater size of carbon crystallites, a higher ordering of the microstructure of carbon and β-SiC and a smaller amount of SiO₂, resulting in electrical and thermal conductivities of 1.17 × 10⁴ Ω⁻¹ m⁻¹ and 25 W/mK, respectively. The thermal conductivity could be further improved to 101 W/mK by increasing the density of the composite to 1.82 g/cm³. In contrast, the pre-treatment at 100 °C produced composites possessing a lower thermal conductivity of 2 W/mK.     

Equivocal Colonic Carcinogenicity of Aloe arborescens Miller var. natalensis Berger at High‐Dose Level in a Wistar Hannover Rat 2‐y Study

ABSTRACT: A 2‐y carcinogenicity study of Aloe, Aloe arborescens Miller var. natalensis Berger, a food additive, was conducted for assessment of toxicity and carcinogenic potential in the diet at doses of 4% or 0.8% in groups of male and female Wistar Hannover rats. Both sexes receiving 4% showed diarrhea, with loss of body weight gain. The survival rate in the 4% female group was significantly increased compared with control females after 2 y. Hematological and biochemical examination showed increase of RBC, Hb, and Alb in the 4% males. The cause of these increases could conceivably have been dehydration through diarrhea. AST and Na were significantly decreased in the males receiving 4%, and Cl was significantly decreased in both 4% and 0.8% males. A/G was significantly increased in the 4% females, and Cl was significantly decreased (0.8%) in the female group. Histopathologically, both sexes receiving 4% showed severe sinus dilatation of ileocecal lymph nodes, and yellowish pigmentation of ileocecal lymph nodes and renal tubules. Adenomas or adenocarcinomas in the cecum, colon, and rectum were observed in 4% males but not in the 0.8% and control male groups. Similarly, in females, adenomas in the colon were also observed in the 4% but not 0.8% and control groups. In conclusion, Aloe, used as a food additive, exerted equivocal carcinogenic potential at 4% high‐dose level on colon in the 2‐y carcinogenicity study in rats. Aloe is not carcinogenic at nontoxic‐dose levels and that carcinogenic potential in at 4% high‐dose level on colon is probably due to irritation of the intestinal tract by diarrhea.     

Adsorptive and photocatalytic removal of phenol by layered niobates organically modified through intercalation and silylation

Layered hexaniobate K4Nb6O17 was modified with dodecylammonium ions and octadecyltrimethoxysilane molecules, which were held in the interlayer spaces by electrostatic interactions and covalent attachment to the layers, respectively. Interlayer spacing of the niobate was expanded by incorporation of the bulky organic species. Vapor adsorption isotherms of benzene and water indicated hydrophobic interlayer microenvironments of the organically modified niobates. Both of the modified niobates fairly adsorbed phenol dissolved in water. The photocatalytic activity of hexaniobate allowed the organically modified materials to photocatalytically decompose phenol upon UV irradiation. Decomposition time courses and quantitative analysis of phenol present in the system indicated that the phenol molecules adsorbed on the niobates were preferentially degraded. XRD and IR analyses of the modified niobates indicated that the silylated niobate was more durable than the ion-exchanged sample; the former kept the structure during the photocatalytic process while the latter was partly collapsed.     

Plate mode propagation losses in solidly mounted resonators

This paper investigates the acoustic losses of propagating eigenmodes through the acoustic mirror of a solidly mounted resonator (SMR) to clarify how resonator properties are influenced by reflection coefficients for the thickness shear (TS) wave as well as that for the thickness extensional (TE) wave. To this end, we analyze the effective acoustic admittance for several test structures with different mirror properties. Leaky modes are distinguished from plate-like modes and the propagation losses are quantified by calculating mode quality factors. The dependence of the propagation properties of leaky eigenmodes is compared with the mirror properties in terms of bulk wave transmission coefficients obtained by the one-dimensional Mason?s model. It is shown that the TE-like main mode couples with TS-like spurious modes, which then influence the leaky loss of the main mode as well. The coupling strength is strongly frequency-dependent and drastically changes with the mirror design. This result explains previous experimental results reported on SMR design.     

Thin films of single-walled carbon nanotubes promote human osteoblastic cells (Saos-2) proliferation in low serum concentrations

One strategy used for the regeneration of bone is the development of cell culture substrates and scaffolds that can control osteoblast proliferation and differentiation. In recent investigations, carbon nanotubes (CNTs) have been utilized as scaffolds for osteoblastic cell cultures; however, there are only a few reports describing the proliferation of osteoblastic cells on thin CNT films; in particular, the effects of serum concentration on cell proliferation have not been studied. In the present study, we prepared culture dishes with homogeneous thin or thick films of non-modified CNTs and examined the effect of serum concentrations on human osteoblastic cells (Saos-2) proliferation in these culture dishes. We demonstrated that the ratio of cell proliferation was strongly affected by the concentration of serum. Interestingly, single-walled carbon nanotube (SWNT) thin films were found to be the most effective substrate for the proliferation of Saos-2 cells in low concentrations of serum. Thus, thin SWNT films may be used as an effective biomaterial for the culture of Saos-2 cells in low serum concentrations.     

Self-Alignment of Optical Devices With Fiber for Low-Cost Optical Interconnect Modules

We propose a novel self-alignment process of optical devices with optical fiber. A vertical-cavity surface-emitting laser (VCSEL) was automatically coupled with a multimode fiber (MMF) through the surface tension of a liquid adhesive within 1.5 s. Misalignment between the center of the VCSEL and the fiber was measured to be 15 mum, which is acceptable for coupling the VCSEL with the MMF. High-speed pulse modulation of the self-aligned VCSEL up to 5 Gb/s, as well as at 1 Gb/s, was demonstrated. The average optical output power was as high as -5.9 dBm at 1 Gb/s.