Co-word analysis of the trends in stem cells field based on subject heading weighting

In this paper, co-word analysis is used to analyze the evolvement in stem cell field. Articles in the stem cell journals are downloaded from PubMed for analysis. Terms selection is one of the most important steps in co-word analysis, so the useless and the general subject headings are removed firstly, and then the major subject headings and minor subject headings are weighted respectively. Then, improved information entropy is exploited to select the subject headings with the experts consulting. Hierarchical cluster analysis is used to cluster the subject headings and the strategic diagram is formed to analyze the evolutionary trends in the stem cell field.     

Nickel-Based Single-Crystal Superalloys (Ni,Co)-Al-(Ta,Ti)-(Cr,Mo, W) Designed by Cluster-Plus-Glue-Atom Model and Their 1000 h Long-Term Ageing Behavior at 900 degrees CEI北大核心CSCD

It has been pointed out recently that the compositions of industrial alloys are originated from cluster-plus-glue-atom structure units in solid solutions. Specifically for nickel-based superalloys, after properly grouping the alloying elements into Al, Ni-like ((Ni) over bar, including Ni, Co, Fe, Re, Ru and Ir), gamma '- forming Cr-like ((Cr) over bar (gamma '), including Ta, Ti, V, Nb), and gamma-forming Cr-like ((Cr) over bar;(gamma), including Cr, Mo and W), the optimal formula for single-crystal superalloys has been established [Al-(Ni) over bar (12)] (Al-1(Cr) over bar (gamma ')(0.5)(Cr) over bar (gamma)(1.5)). In this work, the first generation single-crystal superalloys were investigated on the basis of the proposed formula, by using (Ni) over bar=(Ni and Co), (Cr) over bar (gamma ')=(Ta and Ti), and (Cr) over bar (gamma)=(Cr, Mo and W). Two series of alloys were designed, formulated respectively as group A: [Al-Ni11Co1] (Al1TaxTi0.5-xCr1W0.25Mo0.25), with x=0, 0.25 and 0.5 (the corresponding mass fractions of Ta and Ti are respectively 0Ta-2.65Ti, 4.82Ta-1.26Ti and 9,32Ta-0Ti), and group B: [Al-Ni12-yCo gamma](Al1Ta0.25Ti0.25Cr1W0.25MO0.25), with y=1.5, 1.75, 2 and 2.5 (the corresponding mass fractions of Co are respectively 9.43Co, 11Co, 12.57Co and 15.71Co). The single-crystal superalloys were prepared using selector technique. And then they underwent the following tests of incipient melting, standard heat treatment and 1000 h long term ageing at 900 degrees C. It is found that: (1) In group A, with increasing Ta content (decreasing Ti), all the incipient melting temperatures are increased to above 1330 degrees C, and to the highest value is between 1335 degrees C and 1340 degrees C for alloy 9.32Ta-0Ti; the gamma(')gamma(') lattice negative misfits after standard heat treatment are reduced from -0.262% (0Ta-2.65Ti) to -0.247% (9.32Ta-0Ti); the gamma(') coarsening tendency after long-term ageing is deduced, and alloy 9.32Ta-0Ti has the lowest coarsening rate (K=5.6x10(-5) mu(3)/h). (2) In group B, the Co content does not influence the incipient melting temperature (always above 1330 degrees C) and the coarsening rate of gamma(') after long-term ageing. The major role of Co is to increase the mean size of the gamma(') precipitates to about 0.55 pm and the gamma(') volume fraction to about 69% after the standard heat treatment. These two groups of alloys have their gamma(') coarsening rates approaching the level of third-generation single-crystal superalloys (K approximate to(2.08 similar to 3.82)*10(-5) mu m(3)/h).     

Biomechanics of oral mucosa

The prevalence of prosthodontic treatment has been well recognized, and the need is continuously increasing with the ageing population. While the oral mucosa plays a critical role in the treatment outcome, the associated biomechanics is not yet fully understood. Using the literature available, this paper provides a critical review on four aspects of mucosal biomechanics, including static, dynamic, volumetric and interactive responses, which are interpreted by its elasticity, viscosity/permeability, apparent Poisson''s ratio and friction coefficient, respectively. Both empirical studies and numerical models are analysed and compared to gain anatomical and physiological insights. Furthermore, the clinical applications of such biomechanical knowledge on the mucosa are explored to address some critical concerns, including stimuli for tissue remodelling (interstitial hydrostatic pressure), pressure–pain thresholds, tissue displaceability and residual bone resorption. Through this review, the state of the art in mucosal biomechanics and their clinical implications are discussed for future research interests, including clinical applications, computational modelling, design optimization and prosthetic fabrication.     

低真空循环热电机组与热水锅炉联合供热改造

某热电厂采取部分热电机组低真空循环水直接供热方式,存在剩余部分发电机组排汽余热利用不充分及不利于热网运行调节的问题。为满足增长的供热需求,在对剩余部分发电机组进行低真空改造的基础上,联合热水锅炉,实现热电机组与热水锅炉联合供热方式(采用高温供水、间接连接方式)。     

Terminal-to-Terminal Calling for GEO Broadband Mobile Satellite Communication

Satellite and terrestrial components of IMT?Advanced need to be integrated so that the traditional strengths of each compo?nent can be fully exploited. LTE/LTE?A is now a recognized foundation of terre...     

Correlative High‐Resolution Mapping of Strain and Charge Density in a Strained Piezoelectric Multilayer

A key to strain engineering of piezoelectric semiconductor devices is the quantitative assessment of the strain‐charge relationship. This is particularly demanding in current InGaN/GaN‐based light‐emitting diode (LED) designs as piezoelectric effects are known to degrade the device performance. Using the state‐of‐the‐art inline electron holography, we have obtained fully quantitative maps of the two‐dimensional strain tensor and total charge density in conventional blue LEDs and correlated these with sub‐nanometer spatial resolution. We show that the In_0.15Ga_0.85N quantum wells are compressively strained and elongated along the polar growth direction, exerting compressive stress/strain on the GaN quantum barriers. Interface sheet charges arising from a polarization gradient are obtained directly from the strain data and compared with the total charge density map, quantitatively verifying only 60% of the polarization charges are screened by electrons, leaving a substantial piezoelectric field in each In_0.15Ga_0.85N quantum well. The demonstrated capability of inline electron holography provides a technical breakthrough for future strain engineering of piezoelectric optoelectronic devices.     

碳-芳混杂纤维布加固木梁抗弯性能试验研究

通过碳-芳混杂纤维布加固矩形木梁(杉木和松木)的抗弯性能试验,研究了不同层数的碳-芳混杂纤维布加固矩形木梁的破坏形式、抗弯承载力、荷载-挠度曲线和截面应变分布.试验结果表明:与未加固试件相比,木梁经碳-芳混杂纤维布加固后,其抗弯承载力和刚度有了一定程度的提高,抗弯承载力提高幅度在18.1%～62.0%(松木)和7.7%～29.7%(杉木);刚度提高幅度在13%～21%(松木)和6%～10%(杉木).木梁截面应变沿高度方向的分布基本符合平截面假定.最后,基于试验数据拟合,提出了碳-芳混杂纤维加固木梁抗弯承载力的计算公式.