Low‐temperature sintering and thermal stability of Li2GeO3‐based microwave dielectric ceramics with low permittivity

A low‐permittivity dielectric ceramic Li₂GeO₃ was prepared by the solid‐state reaction route. Single‐phase Li₂GeO₃ crystallized in an orthorhombic structure. Dense ceramics with high relative density and homogeneous microstructure were obtained as sintered at 1000‐1100°C. The optimum microwave dielectric properties were achieved in the sample sintered at 1080°C with a high relative density ~ 96%, a relative permittivity ε_r ~ 6.36, a quality factor Q × f ~ 29 000 GHz (at 14.5 GHz), and a temperature coefficient of resonance frequency τ_f ~ ?72 ppm/^°C. The sintering temperature of Li₂GeO₃ was successfully lowered via the appropriate addition of B₂O₃. Only 2 wt.% B₂O₃ addition contributed to a 21.2% decrease in sintering temperature to 850°C without deteriorating the dielectric properties. The temperature dependence of the resonance frequency was successfully suppressed by the addition of TiO₂ to form Li₂TiO₃ with a positive τ_f value. These results demonstrate potential applications of Li₂GeO₃ in low‐temperature cofiring ceramics technology.     

On some measures for grouping efficiency

One of the traditional methods on managing risk is taken using engineering decisions taken during the project development. In this paper, we propose a new method for risk assessment of a tunnel project where there are three main parameters called taskmaster, adviser, and contractor. The proposed model of this paper is built based on interactive framework of a game theory where, in making decision, each player considers other possible risks choices. We implement three-person cooperative game theory combined with an interactive decision structural model of fuzzy analytical hierarchy process to perform a balance between actions and suitable cooperative strategy for each player. The results reveal that collaboration strategies give the highest outcome for the three players. It also recommends owner managers, design managers, and contractor managers to make collaboration in undertaking innovation while the operator managers need to let an independent organization clearly identify the appropriate risk mitigation measures to be implemented in a timely manner.     

Personality assessment using multiple online social networks

Personality plays an important role in various aspects of our daily life. It is being used in many application scenarios such as i) personalized marketing and advertisement of commercial products, ii) designing personalized ambient environments, iii) personalized avatars in virtual world, and iv) by psychologists to treat various mental and personality disorders. Traditional methods of personality assessment require a long questionnaire to be completed, which is time consuming. On the other hand, several works have been published that seek to acquire various personality traits by analyzing Internet usage statistics. Researchers have used Facebook, Twitter, YouTube, and various other websites to collect usage statistics. However, we are still far from a successful outcome. This paper uses a range of divergent features of Facebook and LinkedIn social networks, both separately and collectively, in order to achieve better results. In this work, the big five personality trait model is used to analyze the five traits: openness to experience, conscientiousness, extroversion, agreeableness, and neuroticism. The experimental results show that the accuracy of personality detection improves with the use of complementary features of multiple social networks (Facebook and LinkedIn, in our case) for openness, conscientiousness, agreeableness, and neuroticism. However, for extroversion we found that the use of only LinkedIn features provides better results than the use of only Facebook features or both Facebook and LinkedIn features.     

Analysis of Frequent Failure of Oil Well Tubings Due to Formation of Longitudinal Slit

In an onshore oil field, many premature tubing failures were observed in wells operating on sucker rod pump. Failures were in the form of longitudinal crack/vertical slit. During last three to four years, the failure frequency had increased and in one well, new tubing vertically cracked in 8 months only. In the internal surface of the tubing, a longitudinal grooving was observed. The shape of the groove resembled the sucker rod and the crack was along the groove. Observation of grooved region under SEM revealed abrasion features typical of mechanical wear. Small corrosion pits were also observed on some portion of grooved region. As the well was vertical, so chance of contact between tubing and sucker rod was low. But tubing was freely suspended in the well, i.e., there was no tubing anchor which made it vulnerable for the buckling. Analytical studies showed that the failed tubing was in buckling region. On comparison of hardness, it was observed that tubing material was softer than the sucker rod. Buckling of the tubing resulted in rubbing of sucker rod against tubing wall due to which tubing had worn out in the form of groove. Wear-oxidation and oxidation-wear of tubing surface at grooved region and corrosive agents of produced water accelerated this material removal process and when the wall thickness of the tubing at groove region reduced to a point where it was not enough to withstand the hoop stresses, a longitudinal crack formed in the grooved region and tubing failed.     

视频转码技术与系统要求相匹配可显著提升新一代视频应用性能

音视频转码曾被视为一种直接的、传统的处理过程,可将源视频编码,生成略差于原始未压缩内容的版本,然后将其重新解码为传输或观看所要求的格式。     

Evidences of solvent‐induced miscibility in polychloroprene‐co‐ethylene‐propene diene terpolymer blends

Solvent dependent changes in the compatibility behavior of Polychloroprene/Ethylene–propylene–diene terpolymer blends (CR/EPDM) have been investigated using dilute solution viscometry and solvent permeability analysis. To predict the compatibility of rubber blends of different compositions in solvents of different cohesive energy densities, Huggins interaction parameter (ΔB), hydrodynamic interaction (Δη) and Sun's parameter (α) were evaluated from the analysis of the specific and reduced viscosity data of two and three‐component polymer solutions. Miscibility criteria were not satisfied for CR/EPDM blends over the entire composition range in toluene, xylene, and carbon tetrachloride (CCl₄), however, a narrow miscibility domain was observed in chloroform (CHCl₃) for CR/EPDM/CHCl₃ system. These results were further corroborated with the analysis of heat of mixing (ΔH_m) and polymer–polymer interaction parameter (χ₁₂), for all rubber blend compositions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Size selection of dispersed,exfoliated graphene flakes by controlled centrifugation

Liquid exfoliation of graphene generally results in flakes with lateral size of one micron or less on average, too small for many applications. In this paper we describe a method to separate an existing dispersion with mean flake length of ～1 μm into fractions, each with different mean flake size. The initial dispersion is centrifuged at a high centrifugation rate, separating small flakes in the supernatant from large flakes in the sediment. Redispersion of the sediment, followed by successive centrifugation, separation and redispersion cycles can be used to separate the flakes by size so long as the centrifugation rate is decreased with each cycle. This procedure results in a range of dispersions with mean flake length varying from 1 μm for the highest final centrifugation rate to 3.5 μm for the sample whose final centrifugation rate was 500 rpm.     

Selective interfacial localization in conducting polycaprolactam/ethylene vinyl acetate/carbon black composites

Unusual electrical conductivity was demonstrated by ethylene vinyl acetate/polycaprolactam/carbon black (CB) composites. The critical exponent value was 1.2 ± 0.2 for ternary composites and was greater than 2.0 for the binary composites, indicating two‐dimensional electrical conduction in ternary composites. The ternary composites also showed inverted U‐shaped conductivity curves when CB weight fraction was greater than 10 wt%. However, at 10 wt% CB, a discontinuous conductivity curve showing conductivity only when polycaprolactam content was greater than 50% was observed, suggesting substantial variation in the interfacial characteristics with the change in the blend composition. Small‐angle X‐ray scattering studies pointed out that ternary composites can be viewed as a two‐phase system with sharp boundaries, and that interface layer in the composites does not exist. Differential scanning calorimetry studies suggested composition dependent variation in the crystallinity of polycaprolactam phase, partially contributing to the increase in the composites' conductivity at higher polycaprolactam fractions. POLYM. COMPOS., 34:912–919, 2013. © 2013 Society of Plastics Engineers     

Polychloroprene rubber/ethylene-propylene diene monomer/multiple walled carbon nanotube nanocomposites: synergistic effects of radiation crosslinking and MWNT addition

Synergistic effect of MWNT induced reinforcement and high energy radiation induced crosslinking on the physico-mechanical and thermal characteristics of polychloroprene rubber (PCR)/ethylene-propylene diene rubber (EPDM)/MWNT elastomeric nanocomposites was investigated. The extent of reinforcement, as assessed using the Kraus equation suggested high reinforcement of the blend on MWNT addition; though, the thermal stability and glass transition of the PCR and EPDM components were not significantly affected by MWNTs. The elastic modulus increased with the radiation dose as well as with the increase in MWNT content. The reinforcing mechanism of the nano-composites was studied by various micromechanics models all of which predicted higher moduli than the experimentally observed results, indicating agglomeration in the nano-composites. Nevertheless, in all the composites synergistic effect of radiation crosslinking and MWNT induced reinforcement were seen, suggesting radiation induced crosslinking between polymer and MWNT interface.