Graphene H-Waveguide for Terahertz Lasing Applications: Electromagnetic Quasi-Linear Theory

A novel graphene H-waveguide is proposed for active terahertz components. A graphene film illuminated by strong pumping light shorts the parallel conductor plates. The terahertz modes propagating along this film are amplified at certain conditions. A rigorous electromagnetic (EM) quasi-linear method of analytical calculations of TEy and TMy eigenmodes is used in this paper to select these conditions. Among them is the use of bound TEy modes interacting with graphene plasmons at frequencies of negative graphene resistance, minimizing conductor loss associated with parallel plates, and excluding the current-crowding effect from the waveguide design. The limitations of the used theory are considered, and the applications of this waveguide are proposed.

Review on Laminated Busbars used in High Frequency Inverters

Improvement in the efficiency and cost in the high frequency inverter will play a major role in its applications like electrical vehicles (EV). A high voltage IGBTs are used in inverters to bear the voltage peaks across the IGBT switch at the turning off period of switch. By decreasing the value of voltage peak, can reduce the voltage rating of IGBT switch, by which the system cost will decrease. Decreasing the value of voltage peak can be achieved by decreasing the inductance of the inverter circuit which includes turned on switch inductance, DC link capacitors inductance and connecting wires inductance. By replacing the connecting wires with a laminated busbar in an inverter, the inductance value of a connecting wires can be reduced. Laminated bus bar is a parallel conductor plates separated by a dielectric medium. Upper plate is considered as positive plate and lower plate is a negative plate. In this paper it gives a detailed information about laminated busbar with different designs, using different conductive materials, their calculated inductance in ANSYS 3D FEM software and concluding with suitable laminated busbar for high frequency inverter.

Students’ knowledge test control in Physics

Controlling learners’ educational achievements in our time performs the most important function of learning. Scientists and methodologists argue that the test control of students’ academic achievement meets the requirements of quantitative and objective measurement of learners’ knowledge, skills and abilities. The relevance of the test controlling method of learners’ academic achievements is dictated also by the introduction of the independent external evaluation (IEE) as a final certification of school leavers. With the emergence of computer classes, the use of tests became available and appropriate. The use of computers in the testing process greatly enhances the benefits of this type of control. This paper is aimed at studying experimentally the impact of the controlling testing on enhancing learners’ educational achievements in Physics and managing learners’ cognitive activity. We have been prepared the system of test questions on the following topics: “We begin to study Physics”, “Mechanical work. Units of work”, “Power and its units”, “Electric current. Conductor Resistance”, “Serial and Parallel Conductor Connection”, “Ideal Gas Laws”, “Atomic Physics. Spectrums”. The tests were developed in order to identify the students’ acquisitions of the main issues constituting the educational material / programme, as opposed to revealing some amount of information from the learner's side. In our opinion, it is important for students to master the level of education that would become the basis for further self-improvement of their own education, their own opportunities to overcome the challenges that the life postures to him / her in today's society. Therefore, the main task while developing the test tasks was the formation of certain subject and life-oriented competences. We conducted a pedagogical experiment to introduce the test control of learners' knowledge in Physics. A series of lessons were conducted using the test survey in the experimental class, but no tests were used in the control class. Using the example of testing 8th grade schoolchildren in Physics it was detected that the use of a systematic test control of knowledge acquisition at corresponding lessons Physics allowed the students to demonstrate better knowledge of certain topics at sufficient and high levels. Keywords: testing control, learners’ self-educational competence in Physics, creative thinking.

In-Plane Thermoelectric Properties of Horizontally Aligned InAs/GaAs Quantum Dot Superlattices

The thermoelectric properties of aligned quantum dot chains are calculated taking in account the change in band structure due to quantum size effects. From the calculated band structure, the Seebeck coefficient and electrical conductivity are calculated in a constant relaxation time approximation (CRTA). The power factor is plotted as a function of the size and spacing of dots and an increase is shown in the power factor for decreasing dot size. The net power factor is calculated using a parallel conductor model. The results are compared to the case of randomly spaced dots which have a power factor calculated using an effective resistance model.