Visualized measurement of extremely high-speed droplets in Venturi scrubber

Venturi scrubbers for filtered venting have been installed in nuclear power plants worldwide. Venturi scrubbers can eliminate fission products from a polluted gas by interaction through gas–liquid interfaces. Therefore, droplet diameter is important from the viewpoint of decontamination. When Venturi scrubbers are used in severe accidents, the gas flow velocity might be extremely high. In these studies, the authors did not measure droplet diameter under extremely high gas velocity conditions. In the scenarios, experimental data pertaining to droplet diameter, under the extremely high gas flow velocity, are required. Therefore, this objective is to evaluate the diameter of extremely high-speed droplets. A visualization experiment was conducted using a Venturi scrubber. The droplet diameter distribution and the Sauter mean diameter (SMD) were determined. By comparing between the experimental value of SMDs and the one evaluated using Nukiyama–Tanasawa equation, it was confirmed that the Nukiyama–Tanasawa equation can be used to evaluate SMD with good accuracy in the gas velocity range of 82–250 m/s, except the highest gas velocity conditions. Furthermore, the droplet generation mechanism in the Venturi scrubber was considered to clarify the main reason why the Nukiyama–Tanasawa equation can be used to evaluate SMD droplet diameter.     

On conditional optimality of a class of learning automata in random environments

In this paper, we develop a new class of learning automata to operate in a random environment with a finite number of responses, called a Q-model, and investigate its asymptotic behavior from the viewpoint of conditional optimality. It is shown that this class contains as a particular case the β-model automaton introduced by Luce, which is available for an environment with binary responses, called a P-model. Making use of the martingale convergence theorem for the asymptotic analysis of the automata, we show that the automata are conditionally optimal, i.e., the automata converge optimally under the restrictions on the probability distributions that characterize the environment. The usefulness of the result is illustrated by its application to two simple automata: the β-model automaton and another one which is also applied to a P-model environment. Then, extending the idea underlying the second automaton, we develop a design method for an effective and structurally simple automaton for any Q-model environment. The conditional optimality of the resulting automaton is also investigated.     

The motion capturing of female divers under water and the trial production of motion viewers for developing a virtual diving experience learning system

The virtual diving experience learning system of “Ama”, Japanese traditional female divers, has been developed to simulate how divers move in a virtual space using the diving interface and utilizing an accelerometer and a gyroscope. This interface not only detects the diving motion but also outputs the movement. Diving motion is shown in the ways of hand motion while standing. Although this makes it possible for a learner to understand the divers’ actions more clearly, this system’s difficulty is in visualizing a divers’ actions including their hands or bodies. Therefore, our study focuses on developing the operation system to reproduce actual ways of Amas’ diving with a virtual human body in a virtual space. First, the motion capture was done in an underwater condition. In the next process, the virtual human body was created. Finally, with the motion viewer, the more vivid actions of the Ama were successfully reproduced much more than in previous attempts. Using this system, the effectiveness of the Amas’ movement learning was confirmed, because a learner practices Amas’ movement.     

Experimental investigation of melt pool behaviour during selective laser melting by high speed imaging

Melt pool behaviour and the characteristics of the surrounding metal powder during selective laser melting (SLM) are captured using high-speed imaging, and the influence of the substrate temperature and the line building sequence on the formation of the built structure and the generation of spatter particles is experimentally investigated. The results indicate that the substrate temperature has a measurable effect on the formation of droplets and the generation of spatter particles, while the volume specific energy density of the process was the principal factor affecting the built structure.     

Success rates in a multimodal command language for home robot users

This article considers the success rates in a multimodal command language for home robot users. In the command language, the user specifies action types and action parameter values to direct robots in multiple modes such as speech, touch, and gesture. The success rates of commands in the language can be estimated by user evaluations in several ways. This article presents some user evaluation methods, as well as results from recent studies on command success rates. The results show that the language enables users without much training to command home robots at success rates as high as 88%–100%. It is also shown that multimodal commands combining speech and button-press actions included fewer words and were significantly more successful than single-modal spoken commands.     

Infrared study of catalytic reduction of lean NOx with alcohols over alumina-supported silver catalyst

Two intense IR absorption bands due to surface isocyanate (-NCO) species have been observed at 2262 and 2232 cm^–1 when an alumina-supported silver catalyst is exposed to a mixture of NO, O₂ and ethanol at 150°C and subsequently heated to > 300°C in vacuum. The intensity of the isocyanate band is hardly affected by the water existing in the mixture. Methanol is less reactive than ethanol for the formation of isocyanate species. The reaction mechanism of catalytic reduction of lean NOx with alcohols is discussed based on these IR spectroscopic findings.     

Preparation of Porous Ceramics with Calcium Metaphosphate Fiber Skeleton for Biomedical Use

High-strength calcium metaphosphate fibers for biomedical applications are extracted from crystallized products of calcium ultraphosphate glasses by aqueous leaching. In the present work, new types of porous ceramics with a skeleton composed of the crystalline fibers are prepared by heating the fibrous products extracted. The fibers in the ceramic are interlinked to each other by glassy phases formed during the heating. This porous material has a large porosity of >60%. The surface of the skeleton can be successfully converted into new calcium phosphate phases such as apatite by heating the porous material treated with a molten salt mixture of CaCl₂-Ca(NO₃)₂.     

Synthesis of Compositionally Homogeneous Sr(CuxZn1−x)1/2W1/2O3

A complex perovskite of Sr(Cu _x Zn_{1- x} )_1/2 W_1/2O₃ (SCZW) is synthesized by a new combination of wet and dry processess. Mixed oxides containing Cu²⁺ and Zn²⁺ (CZ) are prepared by the wet process (coprecipitate method). SCZW is obtained by the dry process (mixed-oxide method) from a mixture of CZ, SrCO₃, and WO₃. SCZW has practically no compositional, unlike solid solutions prepared by the conventional dry method. The wet–dry process method is useful because the wet process is applied to only B-site cations having the same valence.