Hydrodynamic behavior of single particles in a draft-tube bubble column

Velocities of single particles (magnetic tracer particles) were measured in the draft tube region and annular region of a draft-tube bubble columns by use of the magnet-detector coil technique. The relative particle to liquid velocity was also obtained. The observed distribution of particle velocity was broader than that of liquid velocity. The relative particle to liquid velocity depended significantly on superficial gas velocity. Those for the draft tube region had minimums with increasing gas velocity, while those for the annular region decreased monotonously. The effective drag coefficients for the particles were correlated with particle Reynolds number and gas holdup.     

Spatio-Temporal Receptive Field Measurement of Retinal Neurons by Random Pattern Stimulation and Cross Correlation

A method is developed for the measurement of the spatio-temporal receptive field (STRF) of neurons in the retina. The test input is an unsteady visual pattern randomly modulated in both space and time, and the output is the stochastic time course of the intracellular response. The STRF is expressed in terms of the spatio-temporal Wiener kernels calculated through a special cross-correlation algorithm between the response and the stimulus-related information. The method is an extension of existing white-noise identification techniques to include the spatial domain. Consideration is given to the practical implementation of the required stimulus pattern, and has led to several alternative approaches.     

Photonic transport networks based on optical paths

This paper explores the technologies that will enable a further leap forward in transport network evolution. First, requirements of the future transport network are elucidated. Existing network cost is evaluated and the viable means to reduce transport network cost are identified. It is demonstrated that optical path technologies such as WP (wavelength path) and VWP (virtual wavelength path) will play a key role in this. They enhance not only transmission capacity but also cross-connect node throughput cost-effectively by capitalizing on the wavelength routeing scheme. Optical path realization technologies focusing on optical path cross-connect systems are examined. Requirements for the optical path cross-connect system are then elucidated, and a new cross-connect system architecture is evaluated. The architecture exploits PLC (planar lightwave circuit) and other commercially available technologies suitable for large-scale production. The evaluations include cross-connect node upgradability, modular growth capability, total node cost, optical loss and switching power consumption. It is proved that the architecture has significant advantages over existing switch architectures. The optical path technologies provided in this paper will pave the way for a new transport network paradigm, a ubiquitous, bandwidth-abundant and affordable broadband ISDN.     

A Model Study of Stroke Volume Values Calculated from Impedance and Their Relation to the Waveform of Blood Flow

By means of a computer simulation, cardiac stroke volume measured with Kubicek's impedance method (SVz) was evaluated against aortic flow waveform. SVz varied remarkably with the change in the shape of aortic flow-wave whose stroke volume was held constant. SVz was equal to the stroke volume only when the flow-wave was square.     

Dynamic preventive control strategies for power systems considering transient and midterm stabilities

This paper proposes a new dynamic preventive control strategy to maintain power system security, in terms of both transient and midterm stabilities. While the authors have already presented preventive control strategies for transient stability, a new problem has arisen in midterm instability in which some generators lose synchronism after 10 seconds or more from a fault clearance. It is clear that the cause of the instability is mainly post-contingency dynamic steady-state instability. This paper first shows a preventive control strategy for improving midterm stability using a dominant eigenvalue of post-contingency equilibrium point. This paper also presents a unified dynamic preventive control algorithm that can maintain both stabilities together. In this algorithm, the time domain for each stability problem is considered appropriately and the difference between the classical model and the detailed model is analyzed in detail. The effectiveness of the proposed method is examined with numerical examples for a model system.     

Anodic processes on a titanium-supported Ruthenium dioxide electrode at high potentials in a mixture of sulfuric acid and ammonium sulfate

The anodic polarization behaviours of Ti-supported RuO₂ electrode at high potentials and the electrode reactions, especially oxygen evolution and peroxydisulfate ion formation, were investigated in H₂SO₄(NH₄)₂SO₄ mixed aqueous solutions. The effects of NH₄F addition to the solutions on the anodic processes were also examined.The anodic polarization curve is clearly divided into three parts: in the first linear region only oxygen evolution occurs and in the second one peroxydisulfate ion formation takes place, accompanied by oxygen evolution. The transitional region lies between these two linear regions. However, the oxygen evolution reaction proceeds predominantly in all regions in H₂SO₄(NH₄)₂SO₄ mixed aqueous solutions. The current efficiency for peroxydisulfate ion formation depends on the concentration of (NH₄)₂SO₄ and the current density. The current efficiency is greatly increased by adding NH₄F to the mixed solutions. The formation reaction of peroxydisulfate ion in the NH₄F-containing solutions is controlled by the step of the primary discharge of sulfate ion or hydrogensulfate ion.     

Distribution of directional data and fabric tensors

Distribution of directional data is characterized by what is termed fabric tensors. A formal least square approximation is applied, and three kinds of fabric tensors are defined in connection with the choice of a basis of the space of functions on a unit sphere or a unit circle. All the resulting equations are Cartesian tensor equations, and they are interpreted in terms of the representation theory of the rotation group and the potential theory in electrodynamics. It is also shown how this characterization is related to the spherical harmonics expansion or the Fourier series expansion. Finally, a method of statistical test is presented in the Cartesian tensor form to check the true form of the distribution. A physical example is also given to illustrate the proposed technique.     

Performance analysis for the dynamic virtual path bandwidth control method in ATM networks

Broadband ISDN (integrated services digital network) should provide various kinds of communication services for multimedia traffic, including voice, computer data, still picture and motion video, and an ATM (asynchronous transfer mode) technology is expected to satisfy those demands. In ATM networks, a VP (virtual path) concept is introduced for simplifying the network resource management. However, if the bandwidth of each VP is fixed, it cannot absorb traffic load fluctuation. In this case, it is likely to happen that one VP has no remaining bandwidth while other VPs on the same physical link have free capacities. Another extremity is that a VP is not introduced, and that all VCs along the same physical link share the whole bandwidth of the link. This can achieve an efficient use of the link, but it apparently requires complicated call set-up procedures. In this paper, we propose a new dynamic VP bandwidth control method, in which the bandwidth allocated to each VP is dynamically changed according to traffic fluctuation. More specifically, in the case that multiple VPs are multiplexed on the same link between two nodes, when the utilization of some VP is increased, that VP requests an additional bandwidth. When the traffic load becomes low and the utilization of a VP is decreased, a part of the assigned bandwidth is released. We consider two methods for this purpose; one is the basic method in which the bandwidth increase request is issued after the VP bandwidth is exhausted. The other is the look-ahead method where the bandwidth increase is requested in advance before the bandwidth starvation. An approximate analysis for the above methods is provided, and the validation of its accuracy is assessed by comparing with simulation results. Through numerical examples, we show that our methods can provide performance improvement in terms of call loss probabilities of each VP.