A Distributed and Cooperative Environment for Computer Algebra

In this paper, we describe theCentral Control, a software component that enables several symbolic systems to cooperate and exchange data. The Central Control has been designed to be the kernel of an environment for scientific computations which can offer a common and concurrent access to several tools needed by the scientist and the engineer: general purpose and specialized computer algebra systems, visualization tools, links with numerical libraries and tools to manipulate numerical programsetc. The user can interact with the Central Control through one or more (graphical) user interfaces. The Central Control achieves its goals by requiring as little as possible from the tools and by using a particular programming language to provide a unified view for the objects and the operations performed by the connected tools. The Central Control will be used as the basis of theComprehensive Solverthat will provide common access to all the programs developed within the project. We give a simple example of an actual use of the Central Control for computing primary decompositions of ideals.     

Quality optimization of conduction heating foods sterilized in different packages

Heat transfer during the sterilization of conduction heating foods packaged in cylindrical, retort pouch and rectangular containers, was modelled using a finite difference numerical method. Finite surface heat transfer coefficients were considered. Optimal temperatures, defined as the processing conditions that maximize surface or volume average quality retention with the constraint of a target sterility value at the coldest point, were calculated for several types of container. Optimal conditions for several case studies were compared with temperatures estimated by generalized formulae available in literature for the prediction of optimal temperatures as a function of all relevant variables. For all case studies, optimal temperatures predicted in both ways were very similar, with deviations often below ± 1°C. For most packages, the simple-to-use generalized equations, developed for one-dimensional geometries, can therefore be used instead of lengthy numerical calculations involving two- and three-dimensional geometries.     

EFFECT OF SALTING AND SMOKING METHOD ON THE STABILITY OF LIPID AND MICROBIOLOGICAL QUALITY OF NILE PERCH (Lates niloticus)

Nile perch fillets treated with two brine concentrations (250g/L and 80g/L) and smoked by two different methods (hot and cold smoking) were stored at 2C for a period of three weeks. The rate of lipid oxidation during storage was observed to be a function of brine concentration and method of smoking. Lipids were more stable in cold than hot smoked fillet. Total phenolic compounds were inversely correlated with the degree of lipid oxidation. The strength of brine affected the bacterial profile of the stored fish; temperature affected both bacterial growth and lipid oxidation during storage.     

A SEMI-EMPIRICAL APPROACH TO HANDLE BROKEN-LINE HEATING: DETERMINATION OF EMPIRICAL PARAMETERS AND EVALUATION OF PROCESS DEVIATIONS

An existing semi-empirical model for simulating product temperature profiles during thermal processing of conduction or convection heating foods under time varying boundary conditions (variable retort temperatures) was extended for the case of broken-line heating products. The use of the method for determination of the empirical heat penetration parameters for broken-line heating curves as defined by Ball (j_h, f_hl, f_h2, x_bh) was evaluated. Starch solutions, showing broken-line heating behavior, were used as a food simulant.
To investigate the consistency of the determined broken-line heating parameters, and to test the applicability of the method when boundary conditions are time dependent, process deviations consisting of drops on the heating medium temperature during the holding phase of a process were evaluated. The model is a promising approach, if the correct empirical parameters are used.     

CHARACTERIZATION OF [14C]-STARCH DEGRADATION BY RHIZOPUS GLUCOAMYLASE

The hydrolysis of [¹⁴C]-labelled tobacco starch by Rhizopus niveus glucoamylase was investigated using thin-layer and gel filtration chromatography. Hydrolysis was characterized by a period of rapid [¹⁴C]-glucose release, representing 15–30% of the total radioactivity, followed by a prolonged period of slow [¹⁴C]-glucose release. Pullulanase enhanced [¹⁴C]-glucose release, suggesting the presence of α-(1→6) branch points. Thin-layer chromatography was used as a rapid screening method for detecting glucoamylase activity in fractions eluted from a DEAE column of a Thermomyces lanuginosus culture filtrate, and gave results comparable to a coupled enzymatic method. [¹⁴C]-Labelled starch from Canna leaf was less susceptible to amylolytic digestion than [¹⁴C]-labelled tobacco starch.     

INTERVAL-BASED ENVISIONING IN HIQUAL

HIQUAL is a component-oriented deep modeling language that supports the modeling of component hierarchies and the representation and analysis of temporal relations. We describe the semantics of a system of components as a set of temporally and causally related temporal intervals that are denoted by dynamic states and events of the components. Thus, we obtain a uniform semantics for single components, for a system of horizontally connected components at the same level, and for a system of vertically connected components at different levels of abstraction. We claim that in our approach parallelism and other temporal aspects including temporal uncertainty are more naturally represented than in other approaches, in particular those using global state semantics.     

流体力学课程双语教学的实践与思考

文中介绍了外籍教师在北京交通大学进行本科生流体力学课程全英文授课的情况,在双语教学的基本思路、双语教学方法、双语教学效果的考核与评估等方面进行了有益的尝试和探讨,分析了双语教学应注意的问题。实践表明,授课教师是双语教学的关键,进行全英文双语教学不仅能取得预期的专业知识教学效果,还有利于学生了解专业知识的英文描述、表达方法和思维方式,提高学生运用英语进行交流的能力。     

A Statistical, Micromechanical Theory of the Compressive Strength of Brittle Materials

A general theory of the compressive strength of brittle materials is presented. This theory proposes that failure is brought about by structural weakening from accumulated crack damage which increases with the stress level. The statistics of the flaw distribution and the mechanism of crack initiation and extension are important. A sample calculation using the theory is given to demonstrate its application.