ARMA models,their Kronecker indices and their McMillan degree

This paper highlights some difficulties with the use of ARMA models with leading unit coefficient matrix in system identification. It is shown that the McMillan degree of such models is not in any easy way related to the row degrees of the polynomial factors of the ARMA model. A rank test is given for the McMillan degree of such models and it is shown that this degree will generically be a multiple of the dimension of the observation vector.     

Sprayed CdS-Cu2S Solar Cells-2-Preparation of CdS by Airless Spray

Airless spray consists in strongly compressing a liquid in a cylinder fitted with a nozzle. The droplets of liquid which are ejected can be pyrolized on a heated substrate. The technique was applied to the elaboration of CdS-Cu²S photocells. A comparison with classic spray is given. There is an important decrease in energy consumption and spray time and the photocell properties are comparable.     

Physicochemical characterisation of calcium phosphates prepared from milk ultrafiltrates: Effect of the mineral composition

This study deals with the precipitation of calcium phosphate in permeates removed from milks at different pH (6.7, 5.2 and 4.6). An overall high yield of precipitation of calcium and phosphate (70–80%, respectively) was obtained for all precipitates with Ca/P molar ratios close to 1.5. The suspended milk‐derived calcium phosphate (MDCP) precipitates had 8–14 μm size and ?14 to ?28 mV zeta potential. The dried MDCP precipitates were identified as amorphous calcium phosphate (ACP), stable over 18 months of storage at room temperature.     

Vitrification of articular cartilage by high-pressure freezing

For more than 20 years, high-pressure freezing has been used to cryofix bulk biological specimens and reports are available in which the potential and limits of this method have been evaluated mostly based on morphological criteria. By evaluating the presence or absence of segregation patterns, it was postulated that biological samples of up to 600 μm in thickness could be vitrified by high-pressure freezing. The cooling rates necessary to achieve this result under high-pressure conditions were estimated to be of the order of several hundred degrees kelvin per second. Recent results suggest that the thickness of biological samples which can be vitrified may be much less than previously believed. It was the aim of this study to explore the potential and limits of high-pressure freezing using theoretical and experimental methods. A new high-pressure freezing apparatus (Lei?a EM HPF), which can generate higher cooling rates at the sample surface than previously possible, was used. Using bovine articular cartilage as a model tissue system, we were able to vitrify 150-μm-thick tissue samples. Vitrification was proven by subjecting frozen-hydrated cryosections to electron diffraction analysis and was found to be dependent on the proteoglycan concentration and water content of the cartilage. Only the lower radical zone (with a high proteoglycan concentration and a low water content compared to the other zones) could be fully vitrified. Our theoretical calculations indicated that applied surface cooling rates in excess of 5000 K/s can be propagated into specimen centres only if samples are relatively thin (<200 μm). These calculations, taken together with our zone-dependent attainment of vitrification in 150-μm-thick cartilage samples, suggest that the critical cooling rates necessary to achieve vitrification of biological samples under high-pressure freezing conditions are significantly higher (1000–100 000 K/s) than previously proposed, but are reduced by about a factor of 100 when compared to cooling rates necessary to vitrify biological samples at ambient pressure.     

Foaming Properties of Proteins as Affected by Concentration

Commercial sodium caseinate and whey protein isolate were evaluated at protein concentrations 0.25 to 16% with ovalbumin solutions as reference. Logarithmic models were developed to express the effect of protein concentration on foam expansion and serum drainage. The kinetics of gas release from milk protein-stabilized foams followed a three-phase pattern. Low foam collapse rates were observed in initial and final phases while rapid collapse occurred during the transition phase. No transition was observed for ovalbumin-stabilized foams. Globally, foam collapse rate increased with increasing protein concentration. Apparent viscosity of protein-stabilized foams increased with concentration to a maximum; beyond which, a reverse trend was observed. Maximum viscosities of milk protein foams were at concentrations & lt;0.5%, while ovalbumin foams showed maximum viscosity around 2% protein.     

Declarative representation of strategic control knowledge

Strategic (control) knowledge typically specifies how a target task is solved. Representing such knowledge declaratively remains a difficult and practical knowledge engineering challenge. The key to addressing this challenge rests on two observations. One, strategic knowledge comprises two finer types of knowledge: subgoaling knowledge used to construct the goal structure for each problem situation pertaining to a target task, and goal-sequencing knowledge used to choose which subgoal in this goal structure is to be pursued at any given moment. Second, when subgoaling knowledge is explicit and expressed in declarative ontological terms, it is possible to fully express goal-sequencing knowledge in the same declarative terms. Building on these observations, we achieve three things. First, we analyse several conventional knowledge-based applications whose subgoaling and goal-sequencing knowledge is implicit, showing that making their subgoaling knowledge explicit permits (re)representing their goal-sequencing knowledge declaratively. Among the applications analysed are MORE and NEOMYCIN. Second, upon studying the roles of goal-sequencing knowledge vis-á-vis subgoaling knowledge, we develop a declarative formalism for representing goal-sequencing knowledge. Finally, we discuss and illustrate key benefits from using our declarative formalism, including an enhanced ability to validate and reuse goal-sequencing knowledge.     

Stability of discrete systems over a finite interval of time†

In many cases of practical interest there is concern with the behaviour of dynamic systems only over a finite time interval. This concern may arise in one of two ways: In one case the system under consideration is defined over a fixed and finite interval of time, while in the second case the system in question is defined for all time; however, the behaviour of the system is of interest only over a finite time interval.

Recently, Weiss and Infante (1965, 1967) treated the problem of system stability over a finite time interval for the ease of continuous systems. In this paper a theory is developed which concerns itself with the stability of discrete systems over a finite interval of time. The dynamic systems which are considered are general enough so as to include unforced systems, systems under the influence of perturbing forces, linear systems, non-linear systems, time invariant systems, time-varying systems, simple systems and composite systems.

In the present development various definitions of stability are considered and corresponding stability theorems are stated and proved. These theorems yield sufficient conditions for stability and in general involve the existence of Lyapunov-like functions which do not possess the usual definiteness requirements on V and ΔV.     

Multi-agent approach and stochastic optimization: random events in manufacturing systems

We propose a method to solve industrial problems and to take into account random events. It is called the triple coupling. It is based on stochastic algorithms, a simulation model and the multi-agents model of artificial intelligence. The method we propose is easy to use and allows us to take into account most of the constraints found in manufacturing systems. Experts look for solutions to increasing the capacity of production. But the production can be disturbed by random events experienced by the system. Industrial experts need schedules which prevent the consequences of random events. Minimizing such consequences is very important to increasing system delivery. Capital investment is often very high in factories and the cost of the investment goes on regardless of whether the resources are running or not. The multi-agent approach is used to determine schedules for which the consequences of random events are low, and a stochastic algorithm is proposed which permits us to optimize a random variable. We prove that this algorithm finds, with probability one, the schedule of the production for which the consequences of random events are the lowest. We propose to measure the consequences of random events using an influence ratio. Our approach has been used to study the consequences of random events in Peugeot sand foundries of Sept-Fons (France). A benchmark test is presented to prove the efficiency of our solution. For the Peugeot sand foundry of Sept-Fond, random events increase the production time by about 20% compared with the production time without any random events occurring. We have determined schedules of production for which the consequences of random events are about 0.5%.     

Protein Recovery from Veal Bones by Enzymatic Hydrolysis

Enzymatic hydrolysis (commercial enzyme) was applied to crushed bones in a batch reactor. The extraction was modeled using a Doehlert design. The effects of temperature (five levels ranging from 40 to 60°C), pH (seven levels from 5.7 to 7.5), enzyme concentration (seven levels from 20 to 80 g.kg^-1 protein), hydrolysis time (seven levels from 30 to 180 mn) and protein concentration (three levels from 60 to 90 g.kg^-1 mixture) were studied. Response surface methodology (RSM) predicted changes in protein yield and hydrolysis degree. Duration and enzyme concentration were the most important parameters, whereas pH and temperature exhibited no significant effects. Inhibition was observed over 80 g.kg^-1 of protein concentration.