Strengthening of Preloaded RC Beams Using Hybrid Carbon Sheets

Reinforced concrete (RC) beams subject to service loads of 40 or 60% of steel yielding were strengthened using hybrid continuous carbon fiber sheets. The hybrid systems were made of high-strength and high-modulus carbon sheets, and compared with systems using only high-strength carbon. It was found that the use of high-modulus carbon sheets in hybrid systems could increase the yielding load, the flexural stiffness, the postyielding ductility, and reduce the crack opening in concrete. The slope changes on load-deflection curves at steel yielding are not noticeable in hybrid systems. The tensile strains developed in hybrid sheets after the fracture of high-modulus carbon are higher in magnitude and distributed in a larger area, leading to an ultimate carbon fracture with concrete crushing. These unique features are attributed to the high stiffness and low ultimate tensile strain of the high-modulus carbon fibers which stiffen the structures, avoid or delay the fiber-reinforced polymer debonding, and facilitate the deformability during their subsequent breakdown.     

The role of prostate specific antigen in diagnosis of localized adenocarcinoma of the prostate. Nara Uro-Oncology Research Group

The number of cases of prostate carcinoma (PCA) is steadily inceasing in Japan. The clinical application of a reliable tumor marker, prostate specific antigen (PSA) for the diagnosis, as well as the increasing elderly population in Japan may account for this increase. The subjects were patients at the Nara Medical University and its affiliated hospitals; 1) 687 cases without PCA were evaluated for age-specific PSA and the incidence of abnormal PSA following urological manipulations, 2) 135 cases with histological proven BPH by transurethral resection of prostate (TUR-P) were examined for PSA density (PSAD) and positive PSA rate in BPH, 3) 135 cases receiving a needle biopsy with suspicion of PCA were examined for the efficacy of PSA and PSAD and other parameters, and 4) 459 PCA cases treated between 1988 and 1994, were examined for specific PSA and PSAD values by stage and degree of cell differentiation. The PSA assay used in this study was MARKIT-M PA (normal range < or = 3.6 ng/ml). The PSA was decreased gradually with age in non-PCA patients, and abnormal PSA was found in 5.5% of these patients following manipulations. The average PSA was 2.95 +/- 2.03 ng/ml in 130 BPH patients (mean age: 71.1 +/- 7.0 years old. and average prostate volume: 32.9 +/- 16.1 ml). And abnormal PSA level (more than 3.61 ng/ml) was found in 22.3%. The mean PSAD was 0.1.0 +/- 0.06, and PSAD was below 0.15 in 86.1% of these BPH cases. Among the 135 cases receiving a needle biopsy, 33 cases had PSA values between 3.61 and 10.0 ng/ml. Of these cases, PCA was found in 18.5% of the 27 cases with a PSAD below 1.5, and in 33.3% of the 6 cases with a PSAD over 1.5. PSA and PSAD were proportionally increased with stage, and a significant difference in the PSA value was observed between stage B1 and B2, and stage C and D (P < 0.05). However, PSA and PSAD values were not significantly correlated with the cell differentiation in PCA stage A2-C. In total, PSA was 18.1 ng/ml in well, 23.9 ng/ml in moderately and 35.9 ng/ml in poorly differentiated type PCA. The positive rate of PSA was 22.3, 65.4 and 83.5%, that of prostate acid phosphatase (PAP) was 10.0, 17.8 and 45.8%, and that of GSM was 25.0, 14.7 and 68.4%, in BPH, stage A PCA and stage BPCA, respectively. In conclusion, PSA is the most reliable tool in the diagnosis of localized PCA. However, the differential diagnosis of BPH and localized PCA is difficult when the PSA value is between 3.61 and 10.0 ng/ml, and accurate staging of localized PCA is difficult with PSA or PSAD alone. At present, it is necessary to use all possible tools for the early detection of localized PCA, and to perform the needle biopsy in all PCA-suspicious cases.     

Effect of microstructures on dielectric breakdown strength of sintered reaction-bonded silicon nitride ceramics

Silicon nitride (Si₃N₄) was prepared from silicon by a sintered reaction-bonded silicon nitride method using yttria and magnesia as sintering additives. Post-sintering (PS) of nitrided compacts was carried out at 1850°C under a nitrogen pressure of 1 MPa. Effect of PS time on microstructure and dielectric breakdown strength (DBS) of the prepared Si₃N₄ ceramics was evaluated. The DBS was measured using specimens with four different thicknesses (0.30, 0.20, 0.10, and 0.05 mm) in order to examine the thickness dependence. The porosity of the sintered Si₃N₄ decreased by prolonging the PS time, and the full density could be achieved at the PS time of over 6 h. After full densification, rod-like β-Si₃N₄ grains grew up, and their maximum grain size increased from 45.1 to 154.7 μm by prolonging the PS time from 6 to 48 h. The DBS of the thick Si₃N₄ substrates (0.30 mm) showed little variation from 35.4 to 47.0 kV/mm, regardless of the PS time. On the other hand, that of the thin ones (0.05 mm) dramatically decreased from 99.5 to 9.8 kV/mm with increased the PS time from 6 to 48 h. Because the DBS sharply decreased at the thin substrate sintered for longer time in which some large-elongated grains might span the substrate thickness-wise throughout, it was inferred that the interface between β-Si₃N₄ grains and grain boundary phase/intergranular glassy films might be a path of the dielectric breakdown.     

Debye Temperature and Electrical Conduction of Fe2O3-CaO-SiO2 Glasses

The electrical conductivity of iron-containing silica glasses was measured from 80 to 350 K. The conductivity data were analyzed based on the hopping conduction theory. The hopping binding energy (W_p) and disorder energy W_D) were calculated from the activation energy at high and low temperatures. The disorder energy obtained was much lower than reported for FeO-P₂O₅ glasses, but similar to that for vandium-containing glasses.     

Processing Strategy for Producing Highly Anisotropic Silicon Nitride

Silicon nitride with a preferred orientation of large elongated grains was obtained by tape casting of raw powder slurry seeded with rodlike β-Si₃N₄ particles, followed by a gas pressure sintering under 1 MPa nitrogen pressure. The large elongated grains developed from seeds lay in planes parallel to the casting direction in a two-dimensional distribution. Increased fracture toughness (11.1 MPa·m^1/2) and bending strength (1100 MPa) were achieved in the direction perpendicular to the grains alignment compared to specimens with a random distribution of elongated grains. Morover, the specimens exhibited a high Weibull modulus of 46 due to the uniform distribution of large grains.     

High-Strength and High-Fracture-Toughness Ceramics in the Al2O3/LaAl11O18 Systems

Control of microstructure in the Al₂O₃/LaAl₁₁O₁₈ system was performed. Elongated alumina grains were formed by doping with small addition of silica, and 20 vol% lanthana- luminate was formed in situ by the reaction of LaAlO₃- A1₂O₃ in an alumina matrix. Strengths of over 600 MPa and a high fracture toughness (6 MPa.m^1/2) were achieved in the material with both elongated A1₂O₃ grains and LaAl₁₁O₁₈ platelets. Generally antagonistic properties such as strength and fracture toughness have been made compatible in the same ceramic system.     

Preparation of ultrafine polyurethane fiber web by laser‐electrospinning combined with air blowing

Thermoplastic polyurethane fiber webs were prepared using a laser‐heated electrospinning process combined with air blowing. The effect of spinning conditions such as air flow rate and air temperature on fiber diameter and molecular weight was investigated. Although the average fiber diameter decreased with increased air flow rate at each air temperature, the diameter increased when the air flow rate was >15 NL min^?1. In addition, the fiber was comparatively thicker with an increase in the air temperature. The variation in the fiber diameter tends to increase with the air flow rate, and a reduction in the molecular weight of the fiber by thermal degradation was suppressed. The thinnest and most uniform fiber with a diameter of 0.9 µm and a diameter coefficient variation of 15% was obtained at an air temperature of 25°C under an air flow rate of 15 NL min^?1. This fiber also had a minimum of decreased molecular weight. POLYM. ENG. SCI., 54:2605–2609, 2014. © 2013 Society of Plastics Engineers     

Superior performance of non-activated multi-walled carbon nanotube polymer actuator containing ruthenium oxide over a single-walled carbon nanotube

The electrochemical and electromechanical properties of actuators developed using a non-activated multi-walled carbon nanotube (MWCNT)–ionic liquid (IL) gel electrode containing ruthenium oxide (RuO₂) were compared with only-MWCNT and only-single-walled carbon nanotube (SWCNT) based actuators. The double-layer capacitance of the non-activated MWCNT electrode containing RuO₂ was larger than that of the only-MWCNT electrode. The non-activated MWCNT polymer actuator containing RuO₂ surpassed the performance of the only-MWCNT and only-SWCNT actuators in terms of the strain and maximum generated stress. Both MWCNTs and RuO₂ were required to produce large strain and quick response actuators that surpassed the performance of the only-SWCNT polymer actuator and exhibited characteristics sufficient for practical applications (e.g. tactile display).     

Processing and Thermal Conductivity of Sintered Reaction-Bonded Silicon Nitride. I: Effect of Si Powder Characteristics

This paper will present sintered reaction-bonded silicon nitride (SRBSN) material with a high thermal conductivity of 121 W·(m·K)⁻¹, which has been successfully prepared from a coarse Si powder with lower levels of oxygen and aluminum impurities, using a mixture of Y₂O₃ and MgSiN₂ as sintering additives, by nitriding at 1400°C for 8 h and subsequent post-sintering at 1900°C for 12 h at a nitrogen pressure of 1 MPa N₂. This thermal conductivity value is higher than that of the materials prepared from high-purity α-Si₃N₄ powder (UBE SN-E10) with the same additive composition under the same sintering conditions. In order to study the effects of Si powder characteristics on the processing, microstructure, and thermal conductivity of SRBSN, the other type of fine powder with higher native oxygen and metallic impurity (typically Al and Fe) contents was also used. The effects of Si particle size, native oxygen, and metallic impurities on the nitriding process, post-sintering process, and thermal conductivity of the resultant SRBSN materials were discussed in detail. This work demonstrates that the improvement in thermal conductivity of SRBSN could be achieved by using higher purity coarse Si powder with lower levels of oxygen and aluminum impurities. In addition, this work also shows that the nitriding temperature has no significant effect on the microstructure and thermal conductivity of SRBSN during post-sintering, although it does affect the characteristics of RBSN formed during nitridation.     

Synthesis of optical quality ZnO nanowires utilizing ultrasonic spray pyrolysis

ZnO nanowires were grown by an ultrasonic spray pyrolysis technique. The aspect ratio and size of the wire were dependent mainly on the pH value of a precursor solution and the growth temperature. By high-resolution transmission electron microscopic analysis and photoluminescence measurements, it was confirmed that the nanowires are monocrystalline with good optical quality.