Strength development of high strength concretes with and without silica fume under the influence of high hydration temperatures

High performance concretes of high compressive strength are finding increasing applications in many fields of construction such as core walls and columns in tall buildings, long-span bridges and marine structures. In thick cross-sections, the high binder contents of some high strength concretes can result in the development of high in-situ temperatures. The combined influence of limited moist curing and high hydration temperatures may significantly influence the progress of hydration. This can affect the long-term development of in-situ strength and other engineering properties. Knowledge of in-situ strength development under these conditions is needed to ensure safe utilisation of this new generation of construction materials.

This paper presents results of an investigation on the strength development of high strength concretes with and without silica fume subjected to high in-situ temperature conditions. A temperature match conditioning (TMC) system was developed and used to simulate the semi-adiabatic temperature development within medium sized high strength concrete columns. The results of this investigation show that in-situ temperatures of up to 70 °C significantly increased the 7-day strength of a high strength silica fume concrete. Although no strength regression was observed up to 1 year, the silica fume concrete subjected to high early temperatures showed significantly lower strengths when compared to concrete cured at standard temperature. For the silica fume concrete subjected to high early temperatures, non-evaporable water contents suggest little additional hydration beyond 3 days.     

Microscopic spray characteristics in the effervescent atomizer with two aerator tubes

An experimental study is performed on atomization characteristics and stable operating conditions for the injection of high viscous waste vegetable oil using an effervescent atomizer with 2 aerator tubes. Consideration is given to the effects of ALR and liquid viscosity on the velocity and mean diameter of the injected droplet. It is found that (i) as ALR increases, the axial velocity of the droplet is increased, while half-velocity width and SMD are decreased regardless of the change in liquid viscosities, (ii) the rate of fine drop distribution occupied in the total spray field is increased with an increase in ALR, and (iii) the effect of viscosity on the atomization characteristics is minor. Consequently, it is expected that the effervescent atomizer will exhibit an excellent atomization performance at the high ALR condition, regardless of liquid viscosities.     

Calorimetric electron telescope mission: Search for dark matter and nearby sources

We are developing the CALorimetric Electron Telescope, CALET, mission for the Japanese Experiment Module—Exposed Facility, JEM-EF, of the International Space Station, ISS. Major scientific objective is a search for nearby cosmic ray sources and dark matter by carrying out a precise measurement of the electrons in 1 GeV–20 TeV and the gamma-rays in 20 MeV-several TeV. CALET has, moreover, a capability to measure cosmic ray H, He and heavy ions up to 1000 TeV. It will also have a function to monitor the solar activity and the gamma-ray bursts. The phase A study has started on a schedule of the launch in early 2014 by the H-II Transfer Vehicle, HTV, for a 5-year observation.     

Characteristic of an AC chopper circuit with LC filters in the input and output side

LC filters are connected to both the input and output side of the AC chopper circuit in order to remove the switching ripple and harmonics. Characteristics of THD and input power factor are examined by simulation and experiments. When the load is resistive, characteristics are minimally influenced by the filters. In the case of an inductive load, since two poles exist owing to the input and output filters, waveform distortion becomes large. This paper shows that THD can be improved by reducing input filter capacitance. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(2): 45–52, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20304     

Distribution of radionuclides in surface seawater obtained by an aerial radiological survey

We investigated the distribution in seawater of anthropogenic radionuclides from the Fukushima Daiichi Nuclear Power Plant (FNPP1) as preliminary attempt using a rapid aerial radiological survey performed by the U.S. Department of Energy National Nuclear Security Administration on 18 April 2011. We found strong correlations between in-situ activities of ¹³¹I, ¹³⁴Cs, and ¹³⁷Cs measured in surface seawater samples and gamma-ray peak count rates determined by the aerial survey (correlation coefficients were 0.89 for ¹³¹I, 0.96 for¹³⁴Cs, and 0.92 for¹³⁷Cs). The offshore area of high radionuclide activity extended south and southeast from the FNPP1. The maximum activities of ¹³¹I, ¹³⁴Cs, and ¹³⁷Cs were 329, 650, and 599 Bq L^?1, respectively. The ¹³¹I/¹³⁷Cs ratio in surface water of the high-activity area ranged from 0.6 to 0.7. Considering the radioactive decay of ¹³¹I (half-life 8.02 d), we determined that the radionuclides in this area were directly released from FNPP1 to the ocean. We confirm that aerial radiological surveys can be effective for investigating the surface distribution of anthropogenic radionuclides in seawater. Our model reproduced the distribution pattern of radionuclides derived from the FNPP1, although results simulated by a regional ocean model were underestimated.     

Improvement of interfacial layer reliability by incorporation of deuterium into HfAlOx formed by D/sub 2/O-ALD

Deuterium was incorporated into the HfAlOx /SiON gate dielectric by the use of heavy water (D/sub 2/O) instead of H/sub 2/O in the atomic layer deposition (ALD) process of HfAlOx. The HfAlOx formed by D/sub 2/O-ALD acts as a deuterium reservoir, and the deuterium atoms are effectively incorporated into the SiON after full CMOS processing. It is clarified that the deuterium incorporation suppresses interfacial trap generation and interfacial SiON breakdown, while charge-trapping in the HfAlOx bulk traps is barely affected. The D/sub 2/O-ALD process is useful for improving the interfacial layer reliability under gate negative stress; therefore it is not only effective for HfAlOx, but also for high-/spl kappa//SiO/sub 2/(SiON) gate stacks with other high-/spl kappa/ materials such as HfO/sub 2/ or HfSiON.     

Thermal‐fluid transport phenomena in an axially rotating flow passage with twin concentric orifices of different radii

This paper investigates the thermal fluid‐flow transport phenomena in an axially rotating passage in which twin concentric orifices of different radii are installed. Emphasis is placed on the effects of pipe rotation and orifice configuration on the flow and thermal fields, i.e. both the formation of vena contracta and the heat‐transfer performance behind each orifice. The governing equations are discretized by means of a finite‐difference technique and numerically solved for the distributions of velocity vector and fluid temperature subject to constant wall temperature and uniform inlet velocity and fluid temperature. It is found that: (i) for a laminar flow through twin concentric orifices in a pipe, axial pipe rotation causes the vena contracta in the orifice to stretch, resulting in an amplification of heat‐transfer performance in the downstream region behind the rear orifice, (ii) simultaneously the heat transfer rate in the area between twin orifice is intensified by pipe rotation, (iii) the amplification of heat transfer performance is affected by the front and rear orifice heights. Results may find applications in automotive and rotating hydraulic transmission lines and in aircraft gas turbine engines. Copyright © 2005 John Wiley & Sons, Ltd.     

Hydrothermal Synthesis of Novel Smectite-Like Mesoporous Materials

Hydrothermal reaction of slurries made from Si-Mg hydrous oxide and water yielded trioctahedral smectite-like mesoporous materials (SMMs). The OH anion had a marked effect on the properties of SMMs under hydrothermal condition whereas Na cation did not influence SMMs properties. With the increase in synthesis pH at 200°C, pore volume, specific surface area and average pore diameter decreased whereas methylene blue adsorption increased in the pH range of 8.5 to 11.4. Therefore, the SMMs having different layer charges could be synthesized. Both micropore and macropore formation rates decreased with increasing synthesis temperature in the range of 125–200°C and the formation of latter increased over 200°C. As a result, the SMMs synthesized at 200°C from slurries of pH 9.0–9.3 revealed the maximum mesopore formation rate: 0.98 and gave a narrow pore size distribution curve of 3–5 nm. The SMMs were characterized by specific surface areas of 243–679 m² g^-1, pore volumes of 0.20–0.48 cm³ g^-1, average pore diameters of 2.2–5.4 nm and methylene blue adsorption values of 0.16–0.96 meq · g^-1.     

Efficiency improvement of optical fiber wavelength converter without spectral spread using synchronous phase/frequency modulations

We investigate a novel technique to improve the conversion efficiency of optical fiber wavelength converter without spectral spread. It is based on synchronous modulations of the signal phase and the pump phase or frequency, and can suppress not only the stimulated Brillouin scattering (SBS) but also the spread of the converted spectrum.