A new flame retardant synthetic fiber made by an emulsion spinning process

Emulsion spinning has been discussed as a fiber forming process for a long time. At present, however, there are only a few matrix fibers commercially produced in the world. A matrix fiber composed of polyvinyl alcohol and polyvinyl chloride shows excellent flame retardancy which never goes out either by laundering or by dry cleaning and extremely low toxicity of fumes even when forced to burn. This matrix fiber is being used for home furnishings, apparel and industrial fabrics. The coming into force of regulations on children's sleepwear, carpenting, mattresses and blankets in the USA provides this fiber with a great opportunity to open a market into those fields. It has other features including a soft textural feel, moderate moisture regain and abrasion resistance. Special types of this fiber can be vacuum formed by the same manner that is used for thermoplastics molding.     

Studies on chains of bubbles rising through quiescent liquid

The liquid velocity profile induced by a chain of bubbles is studied theoretically and a comparison with measurements is made. The wake velocity and the bubble shape involved in the theoretical development are considered based on the wake theory and the previous empirical relation for single bubbles, respectively. The shape and wake volume of chain bubbles can be treated in the same manner as those of single bubbles by using relative velocity. As a result, using the previous results of the drag coefficient and shape of single bubbles enables the prediction of the rising velocity of chain bubbles.     

Alternating finite automata on ω-words

Alternating finite automata on ω-words are introduced as an extension of nondeterministic finite automata which process infinite sequences of symbols. The classes of ω-languages defined by alternating finite automata are investigated and characterized under four types of acceptance conditions. It is shown that for one type of acceptance condition alternation increases the power in comparison with nondeterminism and for other three acceptance conditions nondeterministic finite automata on ω-words have the same power as alternating ones.     

Fuzzy relational algebra for possibility-distribution-fuzzy-relational model of fuzzy data

In the real world, there exist a lot of fuzzy data which cannot or need not be precisely defined. We distinguish two types of fuzziness: one in an attribute value itself and the other in an association of them. For such fuzzy data, we propose a possibility-distribution-fuzzy-relational model, in which fuzzy data are represented by fuzzy relations whose grades of membership and attribute values are possibility distributions. In this model, the former fuzziness is represented by a possibility distribution and the latter by a grade of membership. Relational algebra for the ordinary relational database as defined by Codd includes the traditional set operations and the special relational operations. These operations are classified into the primitive operations, namely, union, difference, extended Cartesian product, selection and projection, and the additional operations, namely, intersection, join, and division. We define the relational algebra for the possibility-distribution-fuzzy-relational model of fuzzy databases.     

Atomic Layer Epitaxy of Silicon

Two methods are proposed and demonstrated successfully for low temperature atomic layer epitaxy (ALE) of Si, where H atoms play essential roles. The first method is the use of H as a self-limiting factor. Trisilane (Si₃H₈) was used as source gas and the substrate temperature was modulated in order to alternate steps in an ALE cycle. When the temperature was less than 380°C in the adsorption step and more than 520°C in the desorption step, respectively, the grown layer thickness per cycle was 0.8 ML/cycle. The second method is the use of atomic H as an active reducer of a self-limiting factor. A clean surface was exposed to dichlorosilane (SiH₂Cl₂) as source gas to grow an Si monolayer covered with CI. Next, atomic H was injected to reduce CI from the surface. An ideal monolayer growth was obtained with the substrate temperature over 540°C.     

Direct Observation of the Collection Process for Dust Particles from an Air Stream by a Charged Water Droplet

One of the most effective precipitation methods for submicrometer particles is the charged droplet scrubber. The dust collection in the charged droplet scrubber is considered to consist of some processes with respect to the interaction between charged dust particles and a charged water droplet. That is, the charged dust particles are attracted to, collide with, adhere to, penetrate into, rebound from, accumulate on, and reentrain from a charged water droplet. The direct observation of the collection process for dust particles by a charged water droplet was conducted by using the experimental setup designed by the authors. It was found from the experiments that particles with good wettability were captured inside the water droplet, particles with poor wettability floated at regular intervals on the droplet surface, and particles with medium wettability were trapped on or inside the water droplet. When particles were trapped on the droplet surface the growth of dendritic depositions was found, and their behavior was very distinct from those obtained on the fibrous filter due to the fluidity of the droplet surface. The deposition mechanisms of charged particles on the charged water droplet are discussed qualitatively.     

Growth trends of metropolitan areas in Japan: Application of the concept of P-M curve

The aim of this paper is to illuminate basic characteristics of metropolitan areas in Japan. We first delineate the boundaries of ninety-eight Japanese metropolitan areas based on the concept of cut-off point on the P-M curve the idea of which was originally developed by Ogawa in 1957. Secondly, we carry out empirical analyses on spatial structure and growth patterns of those metropolitan areas by use of 1960 and 1975 data. The results of the analyses partly support the theory of urban metamorphosis suggested by Klaassen, Bourdrez and Volmuller in 1981.