Stable detonation wave propagation in rectangular-cross-section curved channels

The detonation propagation phenomena in curved channels were experimentally studied in order to determine the stable propagation condition. A stoichiometric ethylene–oxygen mixture gas and five types of rectangular-cross-section curved channels with different inner radii of curvature were employed. The detonation waves propagating through the curved channels were visualized using a high-speed video camera. Multi-frame short-time open-shutter photography (MSOP) was developed in the present study to simultaneously observe the front shock shape of the detonation wave and the trajectories of triple points on the detonation wave. The detonation wave became more stable under the conditions of a higher filling pressure of the mixture gas and/or a larger inner radius of curvature of the curved channel. The critical condition under which the propagation mode of the detonation wave transitioned from unstable to stable was having an inner radius of curvature of the curved channel (r_i) equivalent to 21–32 times the normal detonation cell width (λ). In the stable propagation mode, the normal detonation velocity (D_n) increased with the distance from the inner wall of the curved channel and approached the velocity of the planar detonation propagating through the straight section of the curved channel (D_str). The smallest D_n was observed on the inner wall and decreased with decreasing r_i/λ. The distribution of D_n on the detonation wave in the stable mode was approximately formulated. The approximated D_n given by the formula agreed well with the experimental results. The front shock shape of the detonation wave could be reconstructed accurately using the formula. The local curvature of the detonation wave (κ) nondimensionalized by λ decreased with increasing distance from the inner wall. The largest λκ was observed on the inner wall and increased with increasing r_i/λ. D_n/D_str decreased with increasing λκ. This nondimensionalized D_n–κ relation was nearly independent of r_i/λ.     

Interlaboratory validation of quantitative duplex real-time PCR method for screening analysis of genetically modified maize

To reduce the cost and time required to routinely perform the genetically modified organism (GMO) test, we developed a duplex quantitative real-time PCR method for a screening analysis simultaneously targeting an event-specific segment for GA21 and Cauliflower Mosaic Virus 35S promoter (P35S) segment [Oguchi et al., J. Food Hyg. Soc. Japan, 50, 117-125 (2009)]. To confirm the validity of the method, an interlaboratory collaborative study was conducted. In the collaborative study, conversion factors (Cfs), which are required to calculate the GMO amount (%), were first determined for two real-time PCR instruments, the ABI PRISM 7900HT and the ABI PRISM 7500. A blind test was then conducted. The limit of quantitation for both GA21 and P35S was estimated to be 0.5% or less. The trueness and precision were evaluated as the bias and reproducibility of the relative standard deviation (RSD(R)). The determined bias and RSD(R) were each less than 25%. We believe the developed method would be useful for the practical screening analysis of GM maize.     

Integrated polarisation beam splitter using waveguide birefringencedependence on waveguide core width

A novel integrated polarisation beam splitter on a silica-based planar lightwave circuit that utilises the waveguide birefringence dependence on waveguide core width is proposed. It was successfully confirmed that the fabricated splitter has a polarisation extinction ratio of >21 dB over a wide wavelength range of 1530 to 1620 nm     

Burst-cluster transmission: service differentiation mechanism for immediate reservation in optical burst switching networks

In this article we propose a service differentiated burst transmission called burst-cluster transmission to provide service differentiation in terms of burst loss for optical burst switching networks. The proposed method consists of a burst assembly algorithm and burst transmission scheduling, and it works only at the ingress edge node. A mixed timer/burst-length-based assembly algorithm is considered for burst assembly, and bursts with different service classes are assembled simultaneously according to the algorithm. A burst-cluster is generated so that the bursts in the cluster are arranged in order from lowest priority to highest. Then the burst-cluster is transmitted according to the burst transmission scheduling. We also consider the application of burst-cluster transmission to delay-sensitive traffic. We evaluate by simulation the performance of the burst-cluster transmission for NSFNET. Numerical examples show that burst-cluster transmission succeeds in providing different service grades even though the burst loss probabilities of high-priority service classes are affected by the traffic load of low-priority ones.     

280 W output power single-ended amplifier using single-die GaN-FET for W-CDMA cellular base stations

A single-ended amplifier using a single-die GaN-FET was successfully developed for W-CDMA cellular base-station systems. The developed amplifier delivers a peak saturated output power of 280 W with a linear gain of 12.6 dB at a drain voltage of 48 V under 2.15 GHz 3GPP W-CDMA signal input. It is believed that the 280 W output power is the record output power in single-ended amplifiers at 2 GHz band. A high drain efficiency of 29% is also obtained at 8 dB power back off from the saturated output power.     

Temperature stability of ultrahigh-speed GaAs JFET ICs

Ultrahigh-speed digital integrated circuits (ICs) implemented with GaAs/int JFETs are confirmed to be reliable in a wide variety of temperatures. Divide-by-256/258 dual-modulus prescaler ICs using source-coupled FET logic (SCFL) circuits that can operate up to 9 GHz have temperature coefficients of operating frequency stability and input power sensitivity of -17.2 MHz/degree and +0.12 dBm/degree between -20 and +100°C, respectively. Direct-coupled FET logic (DCFL) circuits were also confirmed to have very small temperature coefficients. The variations of the maximum operating frequency and the input power sensitivity of the DCFL divide-by-4 divider IC are -1.93 MHz/degree and +0.47 dBm/degree, respectively, between -60 and +100°C. The variation in the threshold voltage of the JFET is -0.88 mV/degree which is very small for the temperature stability of GaAs digital ICs     

An Investigation of the Nanomechanical Properties of 0.5Ba(Ti0.8Zr0.2)O3–0.5(Ba0.7Ca0.3)TiO3 Thin Films

For practical application, the functional piezoelectric film in microelectromechanical systems should meet the requirement of physical properties, as well as the mechanical properties. In this article, 0.5Ba(Ti_0.8Zr_0.2)O₃–0.5(Ba_0.7Ca_0.3)TiO₃ (0.5BZT–0.5BCT) thin films with varied properties were prepared on (100) Si substrates via a sol–gel technique at different annealing temperatures. The effects of the annealing temperature on the morphology, piezoelectricity, hardness, and elastic modulus were studied. Particular attention was paid to the surface frictional behavior of films, and the changes in the friction force can be radically explained in terms of differences in the hardness/elastic modulus ratio and the residual stress of films. And, it reveals that the higher ratio of hardness to elastic modulus and tensile residual stress can contribute to a lower friction force for 0.5BZT–0.5BCT film during sling friction.     

Effect of additives on transesterification activity of Rhizopus chinensis lipase

The transesterification activity of powder lipase prepared from the purified lipase of Rhizopus chinensis cells by freeze-drying was quite low compared with that of acetone-dried cells. Additives which could enhance the transesterification activity of the freeze-dried powder lipase were screened. The freeze-dried lipases prepared with certain fatty acid methylesters or certain types of surfactants exhibited high transesterification activity. It was shown that not only the solubility of the freeze-dried lipase in n-hexane but also the organic solvent-stability was enhanced when methyl stearate was added to the lipase solution at the freeze-drying step.     

Velocity measurements of reactive and non‐reactive flows by NO‐LIF method using NO2 photodissociation

Velocities of reactive and non‐reactive flows, where NO₂ molecules were seeded, were measured by a NO‐based Laser Induced Fluorescence (LIF) method. NO₂ dilute gases were injected from a round tube with an inner diameter of 2 cm and its flow rate was 10 liters/minute or 20 liters/minute. Experiments were performed for 4 conditions—non‐reactive flows of NO₂ dilute gases at two flow rates, an unburnt gas flow of the premixed flame with NO₂ addition, and an unburnt gas flow of the diffusion flame with NO₂ addition. NO molecules were produced in flows by planar emissions of 355 nm laser rays from an Nd:YAG laser system, and NO‐LIF images were taken in a pre‐determined delay. An ICCD camera, a dye laser excited by an excimer laser, and Nd:YAG laser were strictly synchronized by a pulse generator. NO‐LIF signals, which were emitted by photochemically produced NO from NO₂, were strong enough to measure the NO displacements in the case of non‐reactive flows, while with only a few ppm concentrations of NO₂ added it was possible to measure the velocity in detail. Although fluctuations of NO trajectories were observed at the flow rate of 20 liters/minute, instantaneous velocities were measured accurately. In the case of the unburnt gas of the diffusion flame, NO‐LIF signals were also strong, and profiles of NO produced by NO₂ photodissociation were clearly measured. Profiles of NO produced by NO₂ photodissociation in the unburnt gas of the premixed flame were also clearly measured, even in the vicinity of the reaction zone. It can be seen that velocities were measured correctly in the unburnt regions of the premixed and the diffusion flames. With this method, it was possible to measure velocities of both steady and unsteady flows. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(1): 40–52, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20038