Multi-dimensional Evaluation of Recent Neighbourhood Renewal Projects in Beijing: Case Studies on Shichahai and Jinyuchi Neighbourhoods

Most of Chinese cities have experienced a great wave of large-scale neighbourhood renewal in recent years. However, only a few research works have been done in giving assessment after the completion of renewal projects. Aimed at such a circumstance, this paper, by referencing the experience of European countries, establishes a multi-dimensional evaluation framework to analyze the primary data drawn from recent household surveys of Shichahai and Jinyuchi neighbourhoods in Beijing, and puts forward some suggestions based on the conclusions drawn from the surveys.     

Low-pressure,thermo-compressive lamination

Lamination of green ceramic tapes is one of the most important technological processes in multilayer ceramic technology. Lamination affects the quality of all 3D structures (e.g., channels, chambers, membranes, etc.). Novel chemical methods of lamination reduce the deformation of 3D structures. However, these methods are useless in the fabrication of thin membranes and structures with thick-film electronic components or electric vias. Therefore, thermo-compressive lamination is still the best solution for the lamination of green ceramic tapes. Low-pressure thermo-compressive lamination with an insert material is presented in this paper. The influence of pressure and Low Temperature Cofired Ceramics (LTCC) material on the compressibility and shrinkage of LTCC, as well as the influence of the insert material on deflection and distortion of the membranes are presented and discussed in this paper.     

A novel way to fabricate highly porous fibrous YSZ ceramics with improved thermal and mechanical properties

Inspired by nest structure, highly porous fibrous yttria-stabilized zirconia (YSZ) ceramics were fabricated through tert-butyl alcohol (TBA)-based gel-casting process and pressureless sintering by using YSZ fibers as raw material and adding K₂SO₄ as removable sintering aid. Different sintering temperature and soaking time were investigated to achieve optimal thermal and mechanical properties. The results show that all specimens consist of crystallized t-YSZ phase. Fibers interconnect with good interfacial bonding on junctions. Under higher sintering temperature, porosity drops gradually while compressive strength increases significantly. With prolonged soaking time, there is no obvious change in porosity and compressive strength increases gradually. All specimens have uniformly distributed pores with average size of 30.2 μm and show good structural stability at high temperature. Ultra-low thermal conductivity is achieved and ductile fracture mode with high elongation makes it more applicable in high-temperature thermal insulating applications.     

Friction and wear behaviors of dental ceramics against natural tooth enamel

The friction and wear behaviors of dental ceramics against the natural tooth enamel were investigated. In this study three dental ceramics, namely zirconia with both polished and rough surfaces, hot-forged lithium disilicate glass ceramics and silicates based veneer porcelain were involved with two metallic materials, gold–palladium alloy and Nickel–chromium alloy, as references. The tribological tests were carried out under artificial saliva lubrication condition by using freshly extracted natural teeth and samples with controlled surface roughness. The frictional coefficients versus reciprocating cycles were recorded. Scanning Electron Microscopy was used to observe the topography of worn teeth enamel surfaces and antagonists. The frictional coefficient of enamel against gold palladium alloy or Nickel–chromium alloy was the smallest. The frictional coefficient of enamel against polished zirconia or porcelain was between that of metal and glass-ceramic. Upon surface polishing, frictional coefficient between zirconia and enamel was radically decreased. Furrows and granular debris were observed on the worn surfaces of enamel while sliding against the rough zirconia or glass ceramic, indicating a abrasive wear mechanism. While chipping flake and pit-like structure after stripping and crack were observed on the enamel surface while sliding against polished zirconia or Nickel–chromium alloy, indicating a type of fatigue wear. It appeared that the friction and wear performances of zirconia could be improved significantly by adequate surface polishing. This observation indicated that attention must be paid to carefully design proper occlusal surface contours and correctly choose dental materials in clinical practice.     

Identification of asymmetric constitutive laws at high temperature based on Digital Image Correlation

The mechanical characterization of ceramics can be very challenging. Depending on their composition and fabrication process, ceramic materials may exhibit at room temperature different types of mechanical behaviours, ranging from linear elastic to quasi-brittle, like rocks, concrete or plasters. At elevated temperature, they may present a non-linear behaviour, due for instance to the presence of a vitreous phase. However, estimating the evolution of their behaviour from room temperature to elevated temperature is a challenging topic, especially when there is an asymmetry between tension and compression. A methodology based on Digital Image Correlation is presented in this paper where four point bending tests are analysed for temperatures ranging from 25 °C to 900 °C. For a ceramic mainly made of aluminium titanate, the evolution of an asymmetric constitutive law is identified with a strong link with microstructural observations using SEM images.     

Hydrothermal synthesis of PtRu nanoparticles supported on graphene sheets for methanol oxidation in direct methanol fuel cell

Platinum–ruthenium (PtRu) nanoparticles are dispersed on graphene nanosheets and multi-walled carbon nanotubes (MWCNTs) via a hydrothermal method. Transmission electron microsocopy (TEM) observation shows the uniformly dispersed nanoparticles and the average nanoparticle size has been calculated. The electrochemical measurements demonstrate that the Pt–Ru/graphene catalyst exhibits about two times higher mass activity and better tolerance to poisoning species in methanol electro-oxidation than the Pt–Ru/MWCNTs catalyst. This study indicates that the PtRu anodic catalyst synthesized by hydrothermal method can be applied for direct methanol fuel cells (DMFC).     

A bibliometric study of the trend in articles related to eutrophication published in Science Citation Index

A keyword analysis was applied in this work to evaluate research trends of eutrophication papers published between 1991 and 2010 in any journal of all the subject categories of the Science Citation Index compiled by Institute for Scientific Information, Philadelphia, USA. Eutrophication was used as a keyword to search parts of titles, abstracts, or keywords. The published output analysis showed that eutrophication research steadily increased over the past 20 years and the annual publication output in 2008, 2009, 2010 were about four times that of 1991. The whole paper published by China ranked at 3rd, but these papers’ IF were lower than the average of the world. “Water Framework Directive” and “Life Cycle Assessment” were two of the most frequently used author keywords in the period between 1999 and 2010 whilst they did not appear before 1998. These new conception indicated eutrophication research trend was changing to policy and management from technological researches.     

A theoretical study of possible shape and phase changes of carbon nanotube crystals during contraction and expansion

We present a theoretical study of the phase transformations of crystals composed of single wall carbon nanotubes self-assembled by the intertube van der Waals interaction under contraction and expansion, and report a new hexagonal crystal structure caused by expansion of the crystal. We show that when the diameter of the nanotubes is larger than certain critical value, the nanotubes in the crystals will undergo three phase transformations: the closely-packed hexagonal phase I → assembled circular phase → new hexagonal phase II → isolated circular phase. These transformations are proved by both a hybrid atomic-continuum approach and the density functional theory calculations.     

Quantifying helium distribution in dual-ion beam irradiated SiCf/SiC composites by electron energy loss spectroscopy

In this study, we report a method to quantify the helium distribution in the SiC_f/SiC composites, which are used as the first-wall materials of fusion reactor. The helium-bubble formation in Hi-Nicalon Type-S (HNS) was observed in the irradiated SiC_f/SiC composites at a level of 100 dpa and at 800 °C and 1000 °C, respectively. We applied transmission electron microscopy and electron energy loss spectroscopy to investigate the helium-gas-bubbles-formation mechanisms. To simulate the practical first-wall environment of Deuterium–Tritium (D–T) fusion reactor, a dual-ion beam (6 MeV Si³⁺ and 1.13 MeV He⁺) was performed to irradiate the SiC_f/SiC composites. The relationship between the energy shift of He K-edge and the radius of the bubble of the SiC composites was estimated by electron energy loss spectroscopy analysis. The results show that all of the helium atoms irradiated at 1000 °C and formed the bubbles. On the other hand, at 800 °C, only 25.5% of the helium atoms form the helium bubbles. A clear thermal-dependent formation mechanism is found.