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The dynamic (time resolved) PIV (particle imaging velocimetry) measurement technique was applied to high-speed gas flow in a narrow channel with an obstacle. The boundary layer was visualized with a high-speed APX RS camera and an Nd:YLF high repetition double-pulse laser. Nitrogen gas seeded with oil particles using Laskine nozzle flows through a 10 ? 10 mm2 square channel with Reynolds numbers of 11?000 and 34?000. Although a sufficient quantity of images was difficult to capture for the Re = 34?000 flow to visualize the vortex evolution in time for the time resolved analysis of the boundary layer, large scale structures of turbulence at the edge of the thin plate are clearly visualized in the temporal domain. Fluctuation transfer velocities in the boundary layer were measured employing the whole field two-point velocity correlation. It is proposed that dynamic PIV can open a way of measuring the fluctuation transfer velocities in the whole flow target area simultaneously for high-speed turbulent flows even in small scales.

A method for visualizing powder flow in a screw feeder is proposed using x-ray penetration image analysis. With this method, metal minute particle tracers with high absorption ratios are injected into the powder flow, and the motion of tracers is observed using x-ray penetration. This method yields a time series of powder flow images. It is confirmed for powder flow in a screw feeder that the tracer movement ratio agrees well with that of the powder, and a relative density difference of less than 20 times does not cause any distinct problems with tracer response. The visualization method clarified that the powder inside the feeder travels at about one-third the velocity of the screw movement rate along the transmission direction and the powder flow is highly turbulent and loses speed in the region around the screw blade edge.

This paper describes a new high-speed micro PIV technique for measuring both red blood cell velocity and plasma velocity to investigate rheology of blood flow in microcirculation. The measurement system consists of an epi-fluorescent microscope equipped with a high-speed camera with an image intensifier and two sets of colour filters. The technique was applied to in vitro blood flow through a micro round tube of 100 µm diameter. Velocity distributions of dyed red blood cells and plasma seeded with fluorescent particles were obtained separately. The obtained velocity distributions have a high spatial resolution of 9.0 µm × 2.2 µm and high temporal resolution of 6000 Hz.

This paper reports a new technique of micro-resolution particle image velocimetry (PIV). To investigate transient phenomena in a microfluidic device, a high-speed micro-PIV technique was developed by combining a high-speed camera and a continuous wave (CW) laser. The technique was applied to a micro counter-current flow, consisting of water and butyl acetate. The velocity fields of water in the micro counter-current flow were visualized for a time resolution of 500 µs and a spatial resolution of 2.2 × 2.2 µm2. Using the micro-PIV technique, the vortex-like motions of fluorescent particles around the water–butyl acetate interface were captured clearly.

A method for visualizing the spatial distribution of oxygen using particles coated with pressure-sensitive dye is presented. The proposed technique, called the PSParticle method, is a hybrid system combining the technologies of pressure-sensitive paint (PSP) and particle image velocimetry (PIV) and allows the particle velocity and oxygen distribution to be measured simultaneously. As intensity-based imaging is not applicable in this system, a luminescence lifetime-based imaging technique involving double frame imaging is introduced. The system is calibrated and demonstrated in application to measurement of the oxygen distribution in an air jet.

The interaction between chemical reactions and the flow field in microfluidic devices is investigated by a laser-induced fluorescence technique refined for use at microscopic spatial resolution. The pH distribution of chemically reacting flow at a Y-junction in a neutralization reaction in a microfluidic device is successfully visualized at a spatial resolution of 0.89 µm × 0.89 µm.

In this study time-resolved proper orthogonal decomposition (POD) is proposed for the new technique of dynamic (digital) particle image velocimetry (DPIV), and applied to study the coherent structures at the near field of a round jet flow. Time-resolved POD is computed in the radial direction, the axial direction and the temporal domain, in which the turbulence can be easily measured by DPIV. As a result, large-scale vortical structures and their spatial and temporal evolution at the round jet mixing layer are uncovered.

A digital speckle system has been combined with holographic interferometry to improve the accuracy of reconstruction of density distributions. For the combined system, several beam splitters have been used to separate the laser beams from a continuous-wave laser so that measurements can be performed simultaneously by both of the experiments. While the projections of the digital speckle system express the integration of the density gradients, those of the holographic interferometry can be obtained from the integration of the density itself. Thus, the steep region of the projections for the fringe shift of the interferometry has been measured by the use of the digital speckle system more accurately whereas the interferometry has been used to measure the projections for other regions simultaneously. CO2 flow from a rectangular nozzle has been investigated for the proposed combined system.

As endothelial cells are subject to flow shear stress, it is important to determine the detailed velocity distribution in microvessels in the study of mechanical interactions between blood and endothelium. Recently, particle image velocimetry (PIV) has been proposed as a quantitative method of measuring velocity fields instantaneously in experimental fluid mechanics. The authors have developed a highly accurate PIV technique with improved dynamic range. spatial resolution and measurement accuracy. In this paper, the proposed method was applied to images of the arteriole in the rat mesentery using an intravital microscope and high-speed digital video system. Taking the mesentery motion into account, the PIV technique was improved to measure red blood cell (RBC) velocity. Velocity distributions with spatial resolutions of 0.8 x 0.8 microm were obtained even near the wall in the centre plane of the arteriole. The arteriole velocity profile was blunt in the centre region of the vessel cross-section and sharp in the near-wall region. Typical flow features for non-Newtonian fluid were shown. Time-averaged velocity profiles in six cross sections with different diameters were compared.

In order to investigate whether recycling of a metal-organic chemical vapor deposition (MOCVD) precursor, bis(ethylcyclopentadienyl)ruthenium (Ru(EtCp)2), is possible, impurities of used Ru(EtCp)2 collected in a cold trap were analyzed. It became clear that several kinds of organic impurities containing ruthenium (Ru) are contained when analyzing used Ru(EtCp)2 by gas chromatography (GC) mass and liquid chromatography (LC) mass technology. The organic impurities were generated during the course of Ru film formation. When trapped Ru(EtCp)2 was reused as a MOCVD precursor, the surface of the Ru film was somewhat rough. We presumed that organic impurities included in the trapped Ru(EtCp)2 might affect the surface roughness of the Ru film. To remove the impurities, the trapped Ru(EtCp)2 was purified using a purification technology with a 70% recycle rate. The refined Ru(EtCp)2 was found to have a purity and a vapor pressure that were equivalent to those of fresh Ru(EtCp)2. The root-mean-square (rms) roughness value of the Ru film prepared using the refined Ru(EtCp)2 was similar to that of the fresh Ru(EtCp)2. In this paper, we propose that recycling of Ru(EtCp)2, as a MOCVD precursor, is possible.

A form of digital speckle tomography has been proposed for calculating transient three-dimensional density distributions. Multiple CCD images have captured movements of speckles due to the variation in density among three angles of view simultaneously and instantaneously so that asymmetrical and transient flows can be measured. Initially, the variations in density of one-nozzle and two-nozzle test sections have been investigated by the use of a cross-correlation method involving the speckle displacements. The results have been compared with measurements made by Mach-Zehnder interferometry to confirm the accuracy. Then, the speckle movements for downward flow of carbon dioxide from a circular small opening with a vertical partition (CO2-air exchange flow) have been obtained by the cross-correlation tracking method so that those distances can be transformed into deflection angles of laser rays for density gradients. The transient three-dimensional density fields have been reconstructed from the deflection angles by tomography.

An iterative PIV technique in which the combination of the iterative cross-correlation technique and three-point Gaussian peak fitting for a sub-pixel analysis has been used can improve the spatial resolution and accuracy of measurement. It is reported that the root-mean-square (RMS) error of the technique is of the order of only 0.04 pixels. However, a large interrogation window, typically 32×32 pixels or larger, should be taken, resulting in a low resolution, in order to achieve the high sub-pixel accuracy. The high accuracy is not compatible with high spatial resolution. In this paper, a new high-resolution PIV technique based on a gradient method is proposed. Initially, the pixel unit displacement is detected by the iterative method. Then, the sub-pixel displacement is evaluated by the use of the gradient method instead of the three-point Gaussian peak fitting technique. The error of the proposed technique is analytically assessed by Monte Carlo simulations. The RMS error is of the order of 0.01 pixels even with a small interrogation window, for instance 13×13 pixels or less. Thus, the method can achieve high sub-pixel accuracy and high spatial resolution compatibility.

We investigate the electrical conductivity of a TiO2 surface layer on insulators induced by radiation exposure. The surface layer is sufficiently thin to transmit radiation (typically γ-rays) without absorption, but exhibits a current signal indicating the interaction processes of the radiation with substrate insulators. We explain this effect arising from the layered structure and demonstrate a Monte Carlo simulation of photons and electrons to show that electrons generated by irradiation in the substrate travel and cause energy deposition onto the thin layer, envisaging a new type of radiation detector.

The sixth International Symposium on Particle Image Velocimetry (PIV) was held in Pasadena, California, on 21–23 September 2005. The state of the art in many aspects of PIV technology was presented and discussed, and there were 100 oral presentations and 40 posters. PIV is now the standard tool to analyse various flow fields, including micro-flow, nano-flow, high-speed flow, bio-flow and so on. PIV is one of the most successful measurement techniques developed in this decade. Flow field structure can be easily measured with the turn-key PIV system. Nowadays, the targets of PIV research focus on the improvement of accuracy and the application of PIV to complicated nonlinear analysis. This special feature selects five superior papers from the 6th International PIV Symposium. Even though PIV itself is the standard tool, a lot of effort and research is needed to investigate the physics of flow. It will be my pleasure if readers appreciate the hot topics in PIV research as a result of this special feature. The 7th Symposium will be held in Italy in 2007. I hope the progress in PIV research will create a new field of measurement. I would also like to express sincere thanks to the staff at IOPP for their support.

'Molecular Imaging Technology' focuses on image-based techniques using nanoscale molecules as sensor probes to measure spatial variations of various species (molecular oxygen, singlet oxygen, carbon dioxide, nitric monoxide, etc) and physical properties (pressure, temperature, skin friction, velocity, mechanical stress, etc). This special feature, starting on page 1237, contains selected papers from The International Workshop on Molecular Imaging for Interdisciplinary Research, sponsored by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) in Japan, which was held at the Sendai Mediatheque, Sendai, Japan, on 8–9 November 2004. The workshop was held as a sequel to the MOSAIC International Workshop that was held in Tokyo in 2003, to summarize the outcome of the 'MOSAIC Project', a five-year interdisciplinary project supported by Techno-Infrastructure Program, the Special Coordination Fund for Promotion of Science Technology to develop molecular sensor technology for aero-thermodynamic research. The workshop focused on molecular imaging technology and its applications to interdisciplinary research areas. More than 110 people attended this workshop from various research fields such as aerospace engineering, automotive engineering, radiotechnology, fluid dynamics, bio-science/engineering and medical engineering. The purpose of this workshop is to stimulate intermixing of these interdisciplinary fields for further development of molecular sensor and imaging technology. It is our pleasure to publish the seven papers selected from our workshop as a special feature in Measurement and Science Technology. We will be happy if this issue inspires people to explore the future direction of molecular imaging technology for interdisciplinary research.

Research on multiphase flows is very important for industrial applications, including power stations, vehicles, engines, food processing and so on. Multiphase flows originally have nonlinear features because of multiphase systems. The interaction between the phases plays a very interesting role in the flows. The nonlinear interaction causes the multiphase flows to be very complicated. Therefore techniques for measuring multiphase flows are very useful in helping to understand the nonlinear phenomena. The state-of-the-art measurement techniques were presented and discussed at the sixth International Symposium on Measurement Techniques for Multiphase Flows (ISMTMF2008) held in Okinawa, Japan, on 15–17 December 2008. This special feature of Measurement Science and Technology includes selected papers from ISMTMF2008. Okinawa has a long history as the Ryukyus Kingdom. China, Japan and many western Pacific countries have had cultural and economic exchanges through Okinawa for over 1000 years. Much technical and scientific information was exchanged at the symposium in Okinawa. The proceedings of ISMTMF2008 apart from these special featured papers were published in Journal of Physics: Conference Series vol. 147 (2009). We would like to express special thanks to all the contributors to the symposium and this special feature. This special feature will be a milestone in measurement techniques for multiphase flows.

Research on multi-phase flows is very important for industrial applications, including power stations, vehicles, engines, food processing, and so on. Also, from the environmental viewpoint, multi-phase flows need to be investigated to overcome global warming. Multi-phase flows originally have non-linear features because they are multi-phased. The interaction between the phases plays a very interesting role in the flows. The non-linear interaction causes the multi-phase flows to be very difficult to understand phenomena. The International Symposium on Measurement Techniques for Multi-phase Flows (ISMTMF) is a unique symposium. The target of the symposium is to exchange the state-of-the-art knowledge on the measurement techniques for non-linear multi-phase flows. Measurement technique is the key technology to understanding non-linear phenomena. The ISMTMF began in 1995 in Nanjing, China. The symposium has continuously been held every two or three years. The ISMTMF-2008 was held in Okinawa, Japan as the 6th symposium of ISMTMF on 15–17 December 2008. Okinawa has a long history as the Ryukyus Kingdom. China and Japan have had cultural and economic exchanges through Okinawa for more than 1000 years. Please enjoy Okinawa and experience its history to enhance our international communication. The present symposium was attended by 124 participants, the program included 107 contributions with 5 plenary lectures, 2 keynote lectures, and 100 oral regular paper presentations. The topics include, besides the ordinary measurement techniques for multiphase flows, acoustic and electric sensors, bubbles and microbubbles, computed tomography, gas–liquid interface, laser-imaging and PIV, oil/coal/drop and spray, solid and powder, spectral and multi-physics. This volume includes the presented papers at ISMTMF-2008. In addition to this volume, ten selected papers will be published in a special issue of Measurement Science and Technology. We would like to express special thanks to all the participants and the contributors to the symposium, and also to the supporting organizations; The Japanese Society for Multiphase Flow, The Chinese Society for Measurement, National Natural Science Foundation of China, The Chinese Academy of Science, and University of the Ryukyus, Okinawa, Japan. Koji Okamoto Chair of 6th ISMTMF and proceedings editor The University of Tokyo, Japan Yuichi Murai Proceedings co-editor Hokkaido University, Japan

The velocity field and temperature distribution in a fluid flow were measured simultaneously based on luminescence. PIV is useful for velocity measurement, and a measurement method based on the luminescent lifetime is appropriate for detecting the transient temperature field. However, there have been few reports on thermometry in the fluid flow by luminescence, whereas several studies have investigated surface temperature measurement. The europium complex (EuTTA) has been commonly used in temperature-sensitive 'paints' for several years and consequently has been examined in several papers. In the present study, particles doped with EuTTA, called temperature-sensitive particles (TSParticles), were prepared. The optical properties of the TSParticles were investigated. A TSParticle was found to be suitable for use with an optical sensor because its lifetime is very sensitive to temperature changes. The lifetime of the TSParticle was approximately 600 µs at 20 °C in water and the intensity was also large enough to be detected by a CCD camera without any image intensifier, at an exposure time of less than 60 µs. It was found that TSParticles could also be used for velocity measurement by means of the PIV technique. The temperature field was measured based on the decay ratio of the TSParticle images, and the velocity distribution in the same plane was also evaluated from these images by PIV. A demonstration was carried out in a thermal stratified silicone oil bath. The velocity and the transient temperature distribution of the oil flow were successfully measured. The spatial resolution of the temperature measurement in the demonstration was 60 µm. The uncertainty of the temperature was 0.35 °C. The spatial resolution and the uncertainty of velocity measurement were 0.6 mm and 20 µm s−1, respectively.

The measurement of a three-component (3C) velocity field in microfluidic devices with conventional techniques and conventional micro-PIV (particle image velocimetry) is still difficult due to limited optical access. Since Santiago et al (1998 Exp. Fluids 25 316–9), micro-PIV flow velocity measurements have remained mainly limited to 2C velocity vector field realizations. In this study, the third component of the velocity, i.e. out-of-plane velocity extraction from two-dimensional time-resolved (TR) micro-PIV images, is proposed. The method is based on PIV and performs cross-correlation (CC) peak height tracking inside the small ensembles of the TR-PIV flow images. This concept was verified basically by an experiment performed on a microscale fluid flow inside a 100 µm diameter inclined micro tube. Despite the inevitable background noise which affects the measurement negatively, the extracted steady-state depthwise velocity profile was in agreement with the analytical result.

Minority carrier lifetime measurement using a microwave photoconductivity decay method was examined. A simple method of immersing a silicon wafer in a toxic HF solution by using a plastic envelope is introduced. An effective lifetime in 50% HF solution is much higher than that in air due to reduction of the surface recombination velocity and is almost the same compared with that of an oxidized and well-passivated substrate. This method provides the effective lifetime, which approximates a bulk lifetime, without an oxide layer and is useful in estimating the short circuit current of solar cells prior to the cell fabrication.

A 300 W polar axis tracking concentrator with 36 circular Fresnel lenses and cells has been fabricated. Commercial Fresnel lenses are not sufficient for a concentrator, because the cell efficiency is reduced by their non-uniform light distribution. Therefore, a 40×40 cm circular Fresnel lens was designed to obtain the uniform light distribution. As a result of this improvement, the output power becomes about 50% greater than that of the commercial lens. The optical efficiency of the lens is 83%. A 50 mm diameter silicon concentrator cell is n on p type with low bulk resistivity and has a fine radial grid. The output power from a typical concentrator cell is 9.13 W (I sc=18.3 A, V oc=0.666 V, FF=0.749) with 12.0% cell efficiency under 4.7 W/cm2 sunlight at 38°C. The output power from five concentrator units is 253.7 W (I sc=20.6 A, V oc=18.95 V, FF=0.65) with 10.2% total cell efficiency.