Seeking the right balance between three teaching approaches: a quasi-experimental study in the context of learning about thermal phenomena

In this study, we investigated which teaching approach may be optimal to facilitate learning about thermal phenomena in primary school. Concretely, we conducted a pretest-posttest quasi-experiment that included 45 eighth-grade students divided into three groups. In the first group (a non-interactive teacher-centered approach), the teacher gave an experiment-based lecture on converting thermal energy into mechanical work. In the second group (a teacher-centered interactive approach), the teacher gave the same experiments-based lecture, but interacted much more with the students and encouraged them to think about the demonstrations. Finally, in the third group, the student-centered interactive approach was applied. The results of the ANCOVA showed that the three teaching approaches were equally effective in developing students’ understanding of thermal phenomena. However, closer analyses showed that students who learned from the teacher-centered interactive approach significantly outperformed their peers when it came to understanding basic thermal concepts approach, students worked in small groups to conduct the same experiments and “discover” the same relationships that the teacher had introduced in the previous one.

Numerical Model of Current Flow and Thermal Phenomena in Lateral GaN/InGaN LEDs

GaN-based light-emitting diodes (LEDs) became one of the most widely used light sources. One of their key factors is power conversion efficiency; hence, a lot of effort is placed on research to improve this parameter, either experimentally or numerically. Standard approaches involve device-oriented or system-oriented methods. Combining them is possible only with the aid of compact, lumped parameter models. In the paper, we present a new electro-thermal model that covers all the complex opto-electro-thermal phenomena occurring within the operating LED. It is a simple and low computational cost solution that can be integrated with package- or system-oriented numerical analysis. It allows a parametric analysis of the diode structure and properties under steady-state operating conditions. Its usefulness has been proved by conducting simulations of a sample lateral GaN/InGaN LED with the aid of ANSYS software. The results presented illustrate the current density and temperature fields. They allow the identification of ‘hot spots’ resulting from the current crowding effect and can be used to optimise the structure.

Methods of Fast Analysis of DC–DC Converters—A Review

The paper discusses the methods of fast analysis of DC–DC converters dedicated to computer programmes. Literature methods of such an analysis are presented, which enable determination of the characteristics of the considered converters in the steady state and in the transient states. The simplifications adopted at the stage of developing these methods are discussed, and their influence on the accuracy of computations is indicated. Particular attention is paid to the methods of fast analysis of DC–DC converters, taking into account thermal phenomena in semiconductor devices. The sample results of computations of the DC–DC boost type converter obtained with the use of the selected methods are presented. The scope of application of particular computation methods and their duration times are discussed. Computations were performed with the use of SPICE and PLECS.

The thermal phenomena of Aceh tradisional house due to changes inform spatial planning, building materials and constructure structures

The development of science and technology has influenced the pattern of human life, especially the housing as the basic needs in human life. This can also be seen in the Acehnese people who have made changes to their traditional houses which will unwittingly have an impact on the thermal performance of the building.. This study observes the thermal perception of the occupants of the original and changing Aceh traditional houses, in the form of their responses or reactions in describing environmental conditions when the air temperature is hot, normal, or cold, which is carried out by distributing questionnaires. Measurements were made on traditional house buildings and their occupants for 7 (seven) days on each house. As a thermal reference for occupancy, air temperature conditions in buildings and rooms will be measured using a Thermo Hygrograph and a Sling Thermometer. The results of this study indicate that there is a change in the thermal perception of occupancy in the form of a comfort range and length of time when the building is inhabited, which is caused by changes made to the traditional house building, in the form of adding another room at the back without disturbing the main building (Rumoh Aceh) using other materials and different buildings structures (not a stilt house like the main building).

Using statistical inverse methods for detecting defects in electronic components

The thermal modeling of electronic components is mandatory to optimize the cooling design versus reliability. Indeed most of failures are due to thermal phenomena [1]. Some of them are neglected or omitted by lack of data: ageing, manufacturing issues like voids in glue or solder joints, or material properties variability. Transient measurements of the junction-to-board temperature supply real thermal behavior of the component and PCB assembly to complete these missing data[2]. To complement and supplement the numerical model, inverse methods identification based on a statistical deconvolution approach, such as Bayesian one, is applied on these measurements to extract a Foster RC thermal network. The identification algorithm performances have been demonstrated on numerical as well as experimental dataset. Furthermore defects or voids can be detected using the extracted Foster RC networks.

SPICE-Aided Modeling of Daily and Seasonal Changes in Properties of the Actual Photovoltaic Installation

This article proposes a model of an actual photovoltaic installation situated in the Gdynia Maritime University, Poland. This model is formulated in the form of a SPICE network. In the presented model, the influence of selected weather parameters and thermal phenomena on the properties of the components of this installation are taken into account. The structure of the analyzed installation and the form of the formulated model are both presented. By means of this model, values of the power produced by the installation considered in different seasons and different times of the day are computed. The obtained computation results are compared to the measurement results. Good agreement between the results of measurements and computations is obtained. The obtained results of the investigations confirm the considerable influence of weather conditions, as well as daily and seasonal changes in solar irradiation and the ambient temperature, on the electrical energy produced. In the summer months, a decrease in the energy efficiency of the conversion of solar energy into electrical energy in comparison to the winter months is also visible and can even be twofold.

NIR spectroscopy coupled with multivariate data analysis in the prediction of the characteristics of mannitol lyophilized cakes

Mannitol is used in freeze-dried products as a bulking agent, consistency enhancer, or stabilizer, having the lowest hygroscopicity among the excipients commonly used as consistency agents, therefore it can be used in the formulation of unstable preparations. Lyophilization is a complex method of drying a solution at low temperature and low-pressure that addresses especially thermolabile substances, such as proteins. The end-product is a lyophilized powder, which can be administered parenterally after reconstitution with suitable solvents. The objective of this study was to evaluate freeze-dried products obtained from mannitol solutions of different concentrations. Mannitol solutions of increasing concentrations of 2.5%, 5%, 7.5%, and 10% were prepared by dissolving mannitol in distilled water. The prepared solutions were freeze-dried after a preliminary DSC analysis, in which the thermal phenomena that occurred during lyophilization were identified. Freeze-dried preparations were analyzed by different methods: macroscopic analysis by visual assessment and comparison with data from the literature, texture analysis by which several properties of these preparations were studied (hardness, deformation, mechanical work, adhesive strength, fracture resistance, and the number of fractures), evaluation of reconstitution time and porosity. The mannitol used in the lyophilization process, being partially amorphous, required differential calorimetric analysis to establish its glass transition and to avoid the collapse of the preparations during lyophilization. Finally, NIR spectroscopy was used to predict the characteristics of the freeze-dried powders in a non-invasive manner, without prior sample preparation.