Yu.S. Zharkikh, S.V. Lysochenko, B.B. Sus, O.V. Tretyak

Taras Shevchenko National University of Kyiv

PRACTICAL APPROACH IN VIRTUAL EXPERIMENT

Introduction.

Laboratory practice is an integrate part of the educational process in higher education in the study of natural sciences. During laboratory work student receives not only knowledge but also gains skills of his competence as a specialist. In terms of implementing e-learning, the problem of getting educational knowledge is successfully resolved, while the acquisition of experimental skills is requires further consideration. One way to resolution of this problem is to apply in the field of distance learning approaches and principles developed by modern pedagogical science. However, modern computer technologies provide additional opportunities for application of developed pedagogical methods in e-learning [1], promote their development and implementation in practice. In particular the implementation of practical approach in education and the humanization of [1, 2]. Therefore, the laboratory works e-learning should satisfy a number of requirements.

Basic requirements for laboratory work in e-learning.

Student work in electronic laboratory work takes place independently. It has the opportunity to communicate with the teacher by the means of communication. Therefore, one of the main requirements for virtual simulator is using of interactive modes of experiment. Virtual simulator, which uses the ideal models of interactive change of experimental conditions gives to student an opportunity to compare measurements with modern virtual experiments conducted on expensive scientific research equipment and help to learn and understand complex ideas and phenomena [3, 4]. During experiment students learn equipment and techniques of measurement, evaluate the errors, examine statistical appropriateness of results: the influence of data selection on the value of uncertainty, the ratio of random error of measured and instrumental errors, the presence of noise. The configuration of virtual labs can be modified quickly to create new variants of depending on the required academic level.
During virtual laboratory work student must have an impression of work on real equipment. Moreover, "experimental" values of the measured data are taken from the database with the records of real experiment. These "experimental" data are reproduced on a monitor in the form of graphs or tables. In more complex virtual simulators the result of each "observation" is calculated by interpolation with the adding of random errors. Magnitude of error is calculated based on the characteristics of devices used. Step of change of the argument can be various, and its value is approximated to the value of the measurement step of virtual equipment. Random error, given by the teacher or student will be added to result value. Reducing the step of argument and increase of the number of "observations" for averaging increases the precision of the obtained results but increases the time of "experiment".

Student, like in real experiments, has a problem of choosing the conditions that provide the best correlation and accuracy of time "measurements." Results of the experiments are consistently different from one another, and the delay in displaying the data are consistent with time of the modes of research and time of measurement in real equipment. Extrapolation of source data and modeling studies on the reactions of the object influences of experimental factors, especially in critical and emergency modes is required as well. The user interface of the laboratory work can be the same as in real equipment, and the student receives the skills and experience of setting and experiment. Essenital advantage - is the possibility of "increasing the speed of equipment, which allows to explore the effects of different parameters of the experiment on its accuracy in short time. Practice with virtual simulator must initiate creativity and desire for learning to student. For this purpose incentives, monitoring and self learning are used. The most promising way to achieve this is to maximize the principles of interactive applications, a variation of ways of experiment and availability of methods of assessment results stimulating the interest of competition [2, 5] . Development of these approaches approximates remote laboratory work to the real experiment and enables students to acquire skills in real research. Together this allows us to realize and humanize practical approach in education.

Structure of electronic laboratory virtual experiment.

Electronic structure of the virtual experiment includes technical, educational and academic resources [1]. Laboratory works with corresponding methodical tutorials were accumulated in the special developed laboratory. E-learning students could access laboratory through the site which provides access to a virtual laboratory of university. Schedule of research, consultation and tests site is also organized on the site. With the resources necessary for practical e-learning in the modern high school, the most difficult in realization are a remotely carried out laboratory works and virtual simulation with appropriate equipment and software. Therefore, electronic labs may be based in centralized laboratories. Further developed software and databases could be modified according to the needs of different universities and transferred to other learning centers. This exchange facilitates the organization of the laboratory works in high schools that do not have appropriate laboratory facilities. With the availability of an extensive network of electronic laboratory works, one of the options for their content may be entirely virtual simulators, development and creation of which required only a programmer working in collaboration with the teacher.

Software and measurement algorithm in the application of virtual simulators.

Software and measurements algorithms are based on the above requirements formed the basis of laboratory work performed remotely and virtual simulation, based on automated laboratory works for base semiconductor physics. Developed laboratory works can be easily integrated into existing learning process and their implementation are not fundamentally different from conventional automated laboratory work with a computer. Control of experiments is carried out sequentially on separate dialogs, each of which is called with a common user interface. The student makes experimental investigation step by step. At first, the necessary conditions of the experiment are selected in the dialog box of control modules. The results of measurements are displayed in numeric and graphic form and analyzed by student. After the experiment is carried out, all selected data could be stored in a separate file, for the further calculations and report.

For example, we consider the lab work, "Measurement of contact potential difference by the method of the dynamic capacitor”. In this work the measurement of contact potential difference along the surface of silicon wafers with the following calculation parameters such as material lifetime and minority carrier diffusion length. The main window allows to select mode of the experiment, to switch the semiconductor laser light, to change a step value and the number of measurements, to select the delay needed by the stepper motor in moving the sample, to load and save the data, to carry out calculations, to filter of experimental data only those that meet specific criteria. Thus, during work, after scanning the surface of semiconductor wafers, the student must determine the suitability of the results for further mathematical processing.

Then, in a window of the analysis of received data it is possible to build semilogarithmic scale coordinate dependence exp()-1 , where φ_s - shows changes in contact potential difference along the surface of the plate, e - electron charge, k - Boltzmann constant, T - temperature.

For further calculations of free range and time of life of carriers it is necessary to choose linear area on the received dependence and determine the length of displacement and diffusion time of life by the slope of graph. After measurements and calculations, student can compare the result with the listing data and make conclusions. Thereby, during work, the students have to choose optimal parameters of the experiment. Great importance in the development of virtual simulators is the process of obtaining experimental data and virtual measurements. It is known that the gauges are characterized by errors that depend on the magnitude of the measured parameter and range of measurement device. Therefore electronic laboratory work includes calculations that take into account the measurement error, and averaging. The displaying of the results is conducted with a delay typical for the selected equipment. To get the results of measurement the interpolation of input data is carried out and value of error is added. Therefore, for the same input data file results of the two virtual measurements will vary even for the exact same virtual experiment (step change argument and the number of averages). This difference is reduced with the increase of the average results. It becomes close to the data source file, although the time of experiment increases in this case. Lack of measurement accuracy, or lack of required number of averages in virtual measurements can lead to the same difficulties and errors in work as in real measurements. This error may exceed the value of the change of the measured change in the argument by one step.

In the result will be not a monotonic curve with non-existent extremums. This may complicate the further processing of experimental data and lead to errors in subsequent stages. Therefore, the application of a sufficient number of averages and selection step measurements make it possible to obtain results with the required accuracy. At the same time, increasing and decreasing of the step of measurement leads to a corresponding increase of the virtual experiment time. This in turn may increase the measurement time unacceptable and requires an appropriate adjustments. In addition, using of such algorithm of adding data errors in the process of obtaining experimental data help us to avoid the iteration of results. Practically, the result of each measurement, even with the same experiment settings will be different from one another.

Conclusions.
The paper reviews the requirements that applied to remotely carried out laboratory works and virtual simulators. It is shown that work with a virtual simulator allows to select different parameters of the experiment with delays and errors according to used devices and reproduces the conditions typical of real laboratory measurement and imitates a real automated installation.

Application of laboratory work in computer support of the educational process encourage the research skills of students and active approach to learning.

References

1. V.F. Zabolotny. Formuvannya metodychnoi kompetentnosti uchytelya fizyky zasobamy myltymedia Vinnytsya: “Edelveys”, 2009. -456s.

2. Yu.S. Zharkikh, S.V. Lysochenko, A.G. Shkavro, O.V. Tretyak. Gumanitarni aspekty navchannya z zastosuvannyam virtualnyh symulyatoriv laboratornyh robit. // Materially II mezdunarodnoy nauchno-prakticheskoy konferenchii “Kluchevye aspekty nauchnoy deyatelnosti-2007”. Tom 7. - Pedagodika. –Dnepropetrovsk: Nauka i obrazovanie, 2007. s. 7-10. Repenning, A.; Ioannidou, J., “Collaborative use and design of interactive simulations,” in CSCL Proceedings, Stanford, CA, 1999.

3. Corter, J., E.; Nickerson, J., V.; Esche, S., K.;Chassapis, C., “Remote versus hands-on labs: a comparative study”, FIE’04: 34th Annual Conference on Frontiers in Education, vol. 2, Oct 2004, pp. F1G:17–21.

4. Matute H., Vadillo M.A. Assesing e-learning in WEB labs. In L. Gomes & J. Garsia-Zubia {Eds}. Advances on remote laboratories and e-learning experiences. – Bilbao, Spain: University of Deusto, 2007. – p. 97-107.