A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Crystal growth under non-equilibrium conditions can give rise to complex patterns which are generically similar to those found in processes such as viscous fingering, aggregation and electrochemical deposition. Recent theoretical understanding focuses on the interplay between the macroscopic driving force associated with the phase transition and the microscopic interfacial dynamics.

/pdf/the-formation-of-patterns-in-non-equilibrium-growth-1wldk2omnj.pdf

The formation of patterns in non-equilibrium growth

Project-based learning (PBL) is a well-known method for imparting thinking competencies and creating flexible learning environments. Advancing low-achieving pupils is an on-going challenge for educational systems. Routing low-achievers into low-learning tracks creates a vicious circle. In order to extract pupils and their teachers from the on-going cycle of failure, and to promote pupils cognitively and emotionally, four steps were taken: defining significant goals for the pupils as well as for the teachers, changing the learning environment, carrying out original projects taking advantage of the pupils' special skills and abilities, and changing assessment methods for project-based learning activities in a computerized environment. This paper presents a continuous field research that has used qualitative and quantitative tools for exploring pupils' progress in the affective and the cognitive domains. The research tools were: Analysis of pupils' portfolios, observations of class activities, interviews with pupils, teachers and school management, achievements in the matriculation examinations, and assessment of pupils' projects. The findings indicate that scientific-technological PBL elevated pupils' motivation and self-image at all levels and achieved significant affective learning. The activities over three years are summarized and show an increase in the number of students achieving the college admittance requirements. Most of the low-achieving pupils succeeded with distinction in the same matriculation exams that the high-achievers did in the same school.

/pdf/implementation-and-assessment-of-project-based-learning-in-a-pyuw0xe69r.pdf

Implementation and Assessment of Project-Based Learning in a Flexible Environment

As a molten alloy or any multi-component liquid is cooled and solidified the growing solid phase usually forms a porous matrix through which the residual liquid can flow. The reactive two-phase medium comprising the solid matrix and residual liquid is called a mushy layer. Buoyancy forces, owing primarily to compositional depletion as one or more of the components of the alloy are extracted to form the solid phase, can drive convection in the layer. In this review, I present an account of various studies of buoyancy-driven convection in mushy layers, paying particular attention to the complex interactions between solidification and flow that lead to novel styles of convective behavior, including focusing of the flow to produce chimneys: narrow, vertical channels devoid of solid. I define an ‘ideal’ mushy layer and argue that chimneys are an inevitable consequence of convection in ideal mushy layers. The absence of chimneys in certain laboratory experiments is explained in terms of nonideal effects.

/pdf/convection-in-mushy-layers-1wl3koj8s1.pdf

Convection in mushy layers

We present a study of interfacial pattern formation during diffusion-limited growth of Bacillus subtilis It is demonstrated that bacterial colonies can develop patterns similar to morphologies observed during diffusion-limited growth in non-living (azoic) systems such as solidification and electro-chemical deposition The various growth morphologies, that is the global structure of the colony, are observed as we vary the growth conditions These include fractal growth, dense-branching growth, compact growth, dendritic growth and chiral growth The results demonstrate the action of a singular interplay between the micro-level (individual bacterium) and macro-level (the colony) in selecting the observed morphologies as is understood for non-living systems Furthermore, the observed morphologies can be organized within a morphology diagram indicating the existence of a morphology selection principle similar to the one proposed for azoic systems We propose a phase-field-like model (the phase being the bacterial concentration and the field being the nutrient concentration) to describe the growth The bacteria-bacteria interaction is manifested as a phase dependent diffusion constant Growth of a bacterial colony presents an inherent additional level of complexity compared to azoic systems, since the building blocks themselves are living systems Thus, our studies also focus on the transition between morphologies We have observed extended morphology transitions due to phenotypic changes of the bacteria, as well as bursts of new morphologies resulting from genotypic changes In addition, we have observed extended and heritable transitions (mainly between dense branching growth and chiral growth) as well as phenotypic transitions that turn genotypic over time We discuss the implications of our results in the context of the evolving picture of genome cybernetics Diffusion limited growth of bacterial colonies combined with new understanding of pattern formation in azoic systems provide new tools for the study of adaptive self-organization and mutation in the presence of selective pressures We include brief reviews of both the recent developments in the study of interfacial pattern formation in non-living systems and the current trends in the view of mutation dynamics

Adaptive self-organization during growth of bacterial colonies

Dendritic growth of ammonium chloride crystals : Measurements of the concentration field and a proposed nucleation model for growth

A project-based study, the hot-air balloon, was developed to impart both scientific and technological principles to junior high school pupils in Israel. The project exposed pupils to scientific inquiry and the design process in technology. The program was implemented throughout the school year, in a pilot school in the first year and in eight and then ten schools in the second and third year. The science and technology teachers, from varying academic backgrounds, participated in in-service training courses and received individual tutoring in schools. Science and technology studies were both given due consideration, but were not completely integrated. True cooperation between teachers with differing specialties was achieved, because a broad scientific–technological project cannot be taught single-handedly by any one teacher. © 2000 John Wiley & Sons, Inc. Sci Ed84:27–42, 2000.

Hot‐air balloons: Project‐centered study as a bridge between science and technology education

New periodic morphologies observed during dentritic growth of ammonium chloride crystals in thin layers

This review describes the present computer codes used to predict atmospheric transmittance. Since these codes are based on modeling of the optical properties of the atmosphere, there is a constant need to validate them in long-path atmospheric transmittance measurements. These measurements and their results will be described here.

Experimental Validation Of Atmospheric Transmittance Codes

An improved version of a two-wavelength radiometric method is described by which the total water vapor amount along an optical path may be determined by the use of a radiometer and a source at the two ends of the optical path. The method requires two transmission measurements: one at 1.14 microm (at the center of an absorption band) and another at 1.06 microm (an atmospheric window). The spectral transmittance is calculated using the FASCODE computer code, convolved with the source, filter, and detector response curves of the transmissometer. Good agreement (1-7%) is obtained with experimental observations of this quantity as a function of total water vapor amount. The method was verified for horizontal paths of up to 10 km.

Measurement of the integrated water vapor content in the atmosphere by a radiometric method.

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