Crop status evaluations and yield predictions

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Crop status evaluations and yield predictions

A model was developed for predicting the day 50 percent of the wheat crop is planted in North Dakota. This model incorporates location as an independent variable. The Julian date when 50 percent of the crop was planted for the nine divisions of North Dakota for seven years was regressed on the 49 variables through the step-down multiple regression procedure. This procedure begins with all of the independent variables and sequentially removes variables that are below a predetermined level of significance after each step. The prediction equation was tested on daily data. The accuracy of the model is considered satisfactory for finding the historic dates on which to initiate yield prediction model. Growth prediction models were also developed for spring wheat

Science Vocabulary and Teaching

If it should be necessary to relate the work here reported to a theoretical background or to some current problems, such relationships could easily be found in the developing concepts about the psychology and philosophy of the thinking process and in the current discussions concerning critical thinking and the philosophy of science

Crop status evaluations and yield predictions

One phase of the large area crop inventory project is presented. Wheat yield models based on the input of environmental variables potentially obtainable through the use of space remote sensing were developed and demonstrated. By the use of a unique method for visually qualifying daily plant development and subsequent multifactor computer analyses, it was possible to develop practical models for predicting crop development and yield. Development of wheat yield prediction models was based on the discovery that morphological changes in plants are detected and quantified on a daily basis, and that this change during a portion of the season was proportional to yield

The monoclinic phase of PZT ceramics: Raman and phenomenological theory studies

This work reports on the first Raman detection of the tetragonal to monoclinic phase transition in PZT ceramics near morphotropic phase boundary at low temperatures. The transition is characterized by changes in the frequency of lattice modes with the temperature. The results presented here confirm the previous one recently reported by Noheda et al. using high-resolution synchrotron X-ray powder diffraction technique and dielectric measurements. The stability of the new phase is discussed within the framework of phenomenological Landau-Devonshire Theory.Comment: 6 pages including 4 figures, Latex, submitted to Applied Physics Letter

Polarization states of polydomain epitaxial Pb(Zr1-xTix)O3 thin films and their dielectric properties

Ferroelectric and dielectric properties of polydomain (twinned) single-crystal Pb(Zr1-xTix)O3 thin films are described with the aid of a nonlinear thermodynamic theory, which has been developed recently for epitaxial ferroelectric films with dense laminar domain structures. For Pb(Zr1-xTix)O3 (PZT) films with compositions x = 0.9, 0.8, 0.7, 0.6, 0.5, and 0.4, the "misfit strain-temperature" phase diagrams are calculated and compared with each other. It is found that the equilibrium diagrams of PZT films with x > 0.7 are similar to the diagram of PbTiO3 films. They consist of only four different stability ranges, which correspond to the paraelectric phase, single-domain tetragonal ferroelectric phase, and two pseudo-tetragonal domain patterns. In contrast, at x = 0.4, 0.5, and 0.6, the equilibrium diagram displays a rich variety of stable polarization states, involving at least one monoclinic polydomain state. Using the developed phase diagrams, the mean out-of-plane polarization of a poled PZT film is calculated as a function of the misfit strain and composition. Theoretical results are compared with the measured remanent polarizations of PZT films grown on SrTiO3. Dependence of the out-of-plane dielectric response of PZT films on the misfit strain in the heterostructure is also reported.Comment: 23 pages, 4 figure

Atomic Beams

Contains reports on two research projects

Testing, 1, 2, 3, . . . . . . . 10

Teachers are constantly being reminded of the importance of making evaluations of student achievement. Evaluations should be made both for the measurement of the progress of the pupil and for determining the effectiveness of the teacher himself. Methods, tools, and techniques for making these evaluations are topics of common interest and continuous discussion in the teaching fraternity

Do We Need Larger Text-Books?

Current problems in the use of text-books arise from: The continuous production of new knowledge, some basic in concepts or conceptual schemes and some extensions in exciting developments of new devices and applications; but all of them immediately embraced by text-book writers and teachers. Text-books have not become proportionately larger probably because of an irrational belief of most students, parents and even teachers that books should be a relatively small item in the student\u27s budget and textbooks look too big and formidable to the student who thinks of a textbook as a mass of material he must learn, memorizing if necessary, and he is not able to abstract the main or central ideas from what he reads and hears, as will be further documented. An analysis of the current use of textbooks indicates that they are being used in two ways: one is to serve as a survey and overview of a field of knowledge and another as a reference for discussion and study. It is suggested that two different books be used for the two different purposes; one to be more brief and in syllabus form and the other to be larger and a more extensive reference than the present textbooks. In fact it might be well to taboo the use of the term textbook. The author has been using such a system for a large lecture-laboratory course for about the past 10 years and believes that it has been very satisfactory. The system has also been well received by his assisting staff and also by the students. He recommends that others try it and suggests that it can be started easily with the teacher preparing his own outline for his course and using such hard-bound and paperback books as are now available

A Raman Study of Morphotropic Phase Boundary in PbZr1-xTixO3 at low temperatures

Raman spectra of PbZr1-xTixO3 ceramics with titanium concentration varying between 0.40 and 0.60 were measured at 7 K. By observing the concentration-frequency dependence of vibrational modes, we identified the boundaries among rhombohedral, monoclinic, and tetragonal ferroelectric phases. The analysis of the spectra was made in the view of theory group analysis making possible the assignment of some modes for the monoclinic phase.Comment: 5 pages, 4 figure