THERMAL DISPERSION AND HEAT TRANSFER IN NONISOTHERMAL BUBBLE COLUMNS†

Local axial and radial temperatures were measured at steady-state conditions in a 0.078-m-I.D. bubble column heat exchanger. Nitrogen and water superficial velocity ranges were 0-0.6 m/s and 0-0.02 m/s, respectively. Average column pressures were 3.0, 5.1, and 7.1 atm. The axial temperature profile varied significantly with all conditions encountered. Radial temperature profiles were found to be nearly constant, indicating very good radial mixing.

An axial thermal dispersion heat transfer model, capable of representing nonisothermal systems, was employed to characterize the measured bubble column temperature profiles. Thermal dispersion was apparent from large temperature changes in the entrance of the bubble column. Heat transfer coefficients depended on the gas and liquid flow rates. However, the thermal dispersion coefficients depended on linear gas velocity and were a weak function of liquid flow rates. The thermal dispersion coefficients obtained in this study were found to be consistent with other investigations. In addition, they were compared to the mass dispersion coefficients obtained by other studies and found to be in good agreement     

Mathematical Modelling of the Coolness to Touch of Hygroscopic Fabrics

A mathematical model, developed to describe coupled heat and moisture transport in textile materials, has been used to study coolness to the touch and has shown how fibre hygroscopicity influences fabric-temperature responses. The model has been used to explain some earlier experimental observations and was found to give good prediction of the behaviour of fabrics in other skin-fabric-contact experiments. The model has also been applied to the practical wear case in which regular contact between skin and fabric occurs.     

What are X-Machines?

X-machines were introduced by S. Eilenberg in 1974 ([Eil74]) as a mathematical framework for examining the relationships between languages and automata. The X-machine definition provided a very general concept that captured in a simple and elegant way a wide variety of existing models and their computational behaviour. Thus finite state machines, pushdown automata and Turing machines all provided different examples of X-machines obtained by varying some of the components of the X-machine's definition.     

Evolutionary testing using an extended Chaining Approach

Fitness functions derived from certain types of white-box test goals can be inadequate for evolutionary software test data generation (Evolutionary Testing), due to a lack of search guidance to the required test data. Often this is because the fitness function does not take into account data dependencies within the program under test, and the fact that certain program statements may need to have been executed prior to the target structure in order for it to be feasible.This paper proposes a solution to this problem by hybridizing Evolutionary Testing with an extended Chaining Approach. The Chaining Approach is a method which identifies statements on which the target structure is data dependent, and incrementally develops chains of dependencies in an event sequence. By incorporating this facility into Evolutionary Testing, and by performing a test data search for each generated event sequence, the search can be directed into potentially promising, unexplored areas of the test object's input domain.Results presented in the paper show that test data can be found for a number of test goals with this hybrid approach that could not be found by using the original Evolutionary Testing approach alone. One such test goal is drawn from code found in the publicly available libpng library.     

Specification and testing using generalized machines: a presentation and a case study

Although testing is a major part of software development, it rarely gets the attention it deserves from researchers, partly because its foundations are weak and ill-understood. The principal purpose of testing is to detect (and then remove) faults in a software system. However, very few of the existing methods allow the tester to make any precise statement about the type or number of faults that remain undetected after testing is completed. In particular, none of the main techniques used by the software industry can give serious guarantees that a system is fault-free after testing has been completed. This paper advocates the use of a formal method both as a specification language and as the basis of a test data selection strategy. It presents a new method for generating test cases from this type of formal specification that provides a more convincing answer to the problem of detecting all faults in a software system. The method is reductionist in the sense that it guarantees that a system is fault-free provided that its components are fault-free; in turn, the same method could be used to test the resulting sub-systems, so the reduction will continue until the components considered are either known to be correct or are fairly simple pieces of code that can be successfully tested using traditional methods. The formal method used, X-machines, is a blend of finite state machines, data structures and processing functions and provides a simple and intuitive way of specifying computer systems. The use of X-machines as a specification tool and the testing method are illustrated with a case study. © 1998 John Wiley & Sons, Ltd.     

Tribocor 532N as a relatively inert material for use as crucibles/moulds for melting rare-earth alloys

Managed for the US Department of Energy by Martin Marietta Energy Systems, Inc., under contract DE-AC05-84OR21400.     

Complications of latissimus dorsi myocutaneous flap breast reconstruction

Two qualitative rapid appraisal techniques were used in a community-based study to investigate health beliefs, attitudes and practices in a rural district in Nepal. Pregnancy and childbirth remain non-medical activities managed at home. Deaths may be avoided by better access to hospital emergency services. Health awareness of some problems, e.g. oral rehydration and diarrhoeal disease, is high; but of others, e.g. association of haemoptysis with tuberculosis, is poor. These methods require few resources, are efficient in time and manpower required, and generate useful relevant information on a target population. They are recommended for district health development programmes elsewhere.