Gamma-Irradiation of Frozen Kiwifruit Pulp

Frozen (–18°C) de-seeded kiwifruit pulp (Actinidia deliciosa) was irradiated at a dose of 100 krad and stored at -18°C. Irradiation resulted in a 2.11 log₁₀ reduction in aerobic plate count (APC) with bacteria being most susceptible. Molds were less susceptible than yeasts. Assessments carried out over 6 months storage showed no significant differences in physical, chemical and sensory properties between irradiated and nonirradiated pulps. The microbial populations of the pulps decreased in parallel throughout the storage period. Frozen storage without irradiation resulted in a 3 log₁₀ reduction in APC over the 6 months period, a 38% reduction in ascorbic acid, and a slight loss of color. Three days frozen storage (– 18°C) following irradiation resulted in an APC only 0.89 log₁₀ higher than 6 months frozen storage (- 18°C) without irradiation with potential savings in energy and holding times which could have economic benefits.     

Performance analysis of asynchronized synchronous machine†

An asynchronized synchronous machine has two field windings and two special excitation control systems. The paper examines the performance of this type of machine during both synchronous and asynchronous operating conditions. The results illustrate the effects of subsidiary feedback signals in the control loops on equilibrium conditions and stability. They are supported by analysis, which establishes the conditions for stability and shows how these depend on the additional control signals.     

The efficiency and economics of small heterogeneous labour limited queueing systems

This paper presents an evaluation of heterogeneous labour patterns in small, labour limited queueing systems. Three heterogeneous labour patterns, a homogeneous labour force and two labour assignment rules are examined. The experimental systems consist of three machine centres in parallel, each with its own queue. The arrival process is Poisson, and the queue priority rule is first-come-first-served. Each machine centre contains one machine, and the service times are exponentially distributed. The number of labourers is two. The experimental model is a GERTS QR stochastic network simulator. The evaluation focuses upon the relative merits of the various labourer efficiency patterns and offers an economic interpretation of the experimental results.     

Optimal PID automatic voltage regulator for synchronous machines

The design and testing of an optimal PID automatic voltage regulator for synchronous machines is treated. The proposed digital PID regulator combines automatic voltage regulation with the function of a power system stabilizer. The PID and stabilizing signal parameters are optimized based on a linear quadratic performance index using the Simplex method. The design of the regulator is achieved directly without using a linearised mathematical model, and only impulse responses of the system are required during the optimization procedure. The microcomputer-based regulator with digital filters has been tested on a laboratory model turbogenerator system. Simulation and experimental results are presented, showing that the regulator provides very good performance, which is superior to that obtained with a conventional automatic voltage regulator with power system stabilizer.     

THE TYPICALITY OF PHASE TRANSITIONS IN SEARCH

Search is fundamental to artificial intelligence (AI) and numerous sophisticated search methods have been developed. We present a general, simple model of search processes and use it to analytically determine some typical behavior when applied to large problems. In particular, this identifies abrupt changes in overall search cost as small improvements are made in the underlying method. We also examine the robustness of this model's predictions in a range of more realistic cases. More generally, we introduce a criterion for determining when average case results reflect typical behavior which allows the method developed here to be used for investigating other large-scale behaviors of complex AI systems.     

AN IMPROVED SYNERGETIC ALGORITHM FOR IMAGE CLASSIFICATION

A major application of pattern recognition technology is in industrial manufacturing. In this paper, we develop a synergetic algorithm for pattern recognition which is based purely on the appearance of the object, without reference to a CAD model of the object, making the technique generic and flexible. In particular, we apply this algorithm to the problem of classifying an object into a number of user-defined aspects, which is an important problem in robotic manipulation of objects. The technique is fast and can be trained using a non-iterative, deterministic training scheme which will find a zero-error solution on a training set, if such a solution exists.     

SHAPE: A construction algorithm for area placement evaluation

A construction algorithm for the plant layout problem is presented. The problem is formulated as a generalized assignment problem with the objective of minimizing total movement costs. The solution algorithm is a heuristic that utilizes an analogy to the special case of locating one item within a warehouse repetitively for placing and constructing departments. The procedure is sensitive to the departmental areas and approaches the problem as one of area placement. The algorithm provides a large degree of regularity in departmental shape and overall layout outline without having to pre-specify any particular shape. The compact and simple computational nature of the algorithm makes it suitable for adaption to an interactive microcomputer environment.     

A stochastic network simulation model for production line systems†

This paper presents an application of a new network-based simulation model to a class of production line systems and compares this with a closed form procedure. The new model is capable of analysing more realistic production lines by allowing variable work element times (normal and others), parallel stations, in-process inventory, and merging subassembly lines. Furthermore, the model is capable of handling mixed model and batched assembly situations as well as the single product assembly lines. The inclusion of cost and resource options, as integral components makes the model a powerful tool of analysis. The cost option allows evaluation of alternative configurations based on the total cost of the system; whereas, the resource feature enables one to analyse the constrained resource situations. The model can be used to optimize the design of new processing lines and to balance existing lines with a fixed production requirement.     

High temperature acidic stress corrosion of glass fibre composites: Part I Effect of fibre type

The stress corrosion characteristics of uniaxial glass fibre reinforced thermosetting resin composites have been examined in hydrochloric acid at 80°C. A simple technique based on linear elastic fracture mechanics (LEFM) is presented for characterizing crack growth in these materials subjected to hostile acidic environments. The environmental stress corrosion cracking is investigated both for different types of resin and different types of glass fibre reinforcements. Two matrices were used: DERAKANE* 411-45 epoxy vinyl ester resin (based on Bisphenol-A epoxy resin) and DERAKANE 470-30 epoxy vinyl ester resin (based on epoxidized novolac resin). Two glass fibre types were employed: standard E-glass fibre and ECRGLAS®, a special type of E-glass with superior acid resistance. Model experiments using a modified double cantilever beam test with static loading have been carried out on unidirectional composite specimens in 1 M hydrochloric acid solution at 80°C. The rate of crack growth in the specimen depends on the applied stress, the temperature and the environment. Consequently, the lifetime of a component or structure made from glass fibre reinforced plastics (GRP) subjected to stress corrosion conditions, could be predicted provided the dependence of crack growth rate on stress intensity at the crack tip is known. Scanning electron microscope studies of the specimen fracture surfaces have identified the characteristic failure mechanisms. The most important finding of this work is that the selection of DERAKANE epoxy vinyl ester resins reinforced with ECRGLAS® fibre exhibited superior resistance to crack growth at 80°C compared to similar E-glass reinforced composites at room temperatures.     

Application of multivariable frequency response methods to control of turbogenerators

This paper deals with the design, evaluation and testing of an integrated control scheme for a turbogenerator equipped with a high-gain thyristor exciter and an electro-hydraulio governing system. Multivariable frequency response methods are used, and these are demonstrated to be eminently suitable for the design and analysis of turbogenerator controllers. It is shown that a control scheme consisting of an automatic voltage regulator with speed stabilizer, and speed governor with lead compensator, designed by the above methods, can greatly improve the dynamic and transient performance of a turbogenerator.

This was confirmed by computer simulation, and by extensive tests on a laboratory model turbogenerator. The controllers in the oxcitor and governor loops are easily implemented, and the results show significant improvements in system damping, transient stability, and post-fault recovery of terminal voltage. It has thus been established that these controllers, designed on the basis of linearized mathematical models, work well in practice, at least in a laboratory environment.