Influence of the Geometry of Beveled Edges on the Stress-Strain State of Hydraulic Cylinders

The studies were carried out to determine the influence of forms obtained when preparing edges for welding a cylinder for hydraulic legs; the maximum stresses were defined at the location of weld roots, depending on variable parameters. The stress-strain states were calculated using finite element method

An efficient emotion classification system using EEG

Emotion classification via Electroencephalography (EEG) is used to find the relationships between EEG signals and human emotions. There are many available channels, which consist of electrodes capturing brainwave activity. Some applications may require a reduced number of channels and frequency bands to shorten the computation time, facilitate human comprehensibility, and develop a practical wearable. In prior research, different sets of channels and frequency bands have been used. In this study, a systematic way of selecting the set of channels and frequency bands has been investigated, and results shown that by using the reduced number of channels and frequency bands, it can achieve similar accuracies. The study also proposed a method used to select the appropriate features using the Relief F method. The experimental results of this study showed that the method could reduce and select appropriate features confidently and efficiently. Moreover, the Fuzzy Support Vector Machine (FSVM) is used to improve emotion classification accuracy, as it was found from this research that it performed better than the Support Vector Machine (SVM) in handling the outliers, which are typically presented in the EEG signals. Furthermore, the FSVM is treated as a black-box model, but some applications may need to provide comprehensible human rules. Therefore, the rules are extracted using the Classification and Regression Trees (CART) approach to provide human comprehensibility to the system. The FSVM and rule extraction experiments showed that The FSVM performed better than the SVM in classifying the emotion of interest used in the experiments, and rule extraction from the FSVM utilizing the CART (FSVM-CART) had a good trade-off between classification accuracy and human comprehensibility

Scientific, institutional and personal rivalries among Soviet geographers in the late Stalin era

Scientific, institutional and personal rivalries between three key centres of geographical research and scholarship (the Academy of Sciences Institute of Geography and the Faculties of Geography at Moscow and Leningrad State Universities) are surveyed for the period from 1945 to the early 1950s. It is argued that the debates and rivalries between members of the three institutions appear to have been motivated by a variety of scientific, ideological, institutional and personal factors, but that genuine scientific disagreements were at least as important as political and ideological factors in influencing the course of the debates and in determining their final outcome

Low-cost photovoltaic emulator for instructional laboratories

This paper discusses a simple and cheap PV emulator based on a linear power supply that does not require a source of light to conduct laboratory experiments. The emulator has been designed to underpin students' understanding the properties of PV cell V-I characteristics and the ways to maximise the output power learned from lectures, tutorial and self-studies. The emulator has been built using “on the shelf” components and tested under rated power conditions. It demonstrated a good emulation of V-I characteristics within the rated range of the sun irradiation and the temperature

Review of fast square root calculation methods for fixed point microcontroller-based control systems of power electronics

Square root calculation is a widely used task in real-time control systems especially in those, which control power electronics: motors drives, power converters, power factor correctors, etc. At the same time calculation of square roots is a bottle-neck in the optimization of code execution time. Taking into account that for many applications approximate calculation of a square root is enough, calculation time can be decreased with the price of precision of calculation. This paper analyses existing methods for fast square root calculation, which can be implemented for fixed point microcontrollers. It discusses algorithms’ pros and cons, analyses calculation errors and gives some recommendations on their use. The paper also proposes an original method for fast square root calculation, which does not use hardware acceleration and therefore, is suitable for implementation at a variety of modern Digital Signal Processors, which have high-speed hardware multipliers, but do not have effective dividers. The maximum relative error of the proposed method is 3.36% for calculation without division, and can be decreased to 0.055% using one division operation. Finally, the most promising methods are compared and results of their performance comparisons are depicted in tables.

Review of electrically powered propulsion for aircraft

This paper presents a review of the state-of-the-art in aircraft electrical propulsion technology. A comparison is provided of differing propulsion mechanisms such as propellers, open fans, ducted fans, multi-stage rim driven fans and distributed thrust designs and their suitability to particular flight profiles and mission applications. Electrical motor architectures are also reviewed with particular attention being given to synchronous machines, such as Brushless Direct Current (BLDC) and Switched Reluctance Motor (SRM) technologies, and the recent advances that have been made in solid-state switching and High Temperature Superconducting (HTS) material applications. Present day electrical power generation, storage and control technologies are also reviewed including hybrid and fuel cell technologies and regeneration techniques. Electrical storage capabilities with regard to specific power and energy characteristics are discussed and the extent to which existing system technology can be integrated onto a Hybrid-electric and an All Electric Aircraft (AEA) is also investigated. Finally, a conclusion is provided highlighting the current technological challenges facing the development of commercial aircraft in terms of performance, airframe configuration and legislative and operational infrastructural requirements

A review of electrical motor topologies for aircraft propulsion

This paper provides a review of the state-of-the art in aircraft electrical propulsion (AEP). Initially, the limitations of on-board energy storage devices are highlighted and contextualised. The definitions of useful measures for determining the suitability of motor design, namely specific power and motor torque per unit rotor volume (TRW), are discussed and relevant examples are provided. The classifications of motors used for terrestrial vehicle applications are reviewed and their limitations highlighted regarding their suitability to AEP applications. A discussion on motor configurations for aerospace applications is provided which includes: synchronous motor stator winding configurations; axial flux motor configurations and the causes of energy losses. Additionally, the topologies and performance characteristics of existing aerospace motor technologies are examined. It was concluded that electrical motors provide an ideal means for achieving aircraft propulsion and that higher motor speeds are likely to be required for future commercial aircraft motor designs

Modelling of a photovoltaic array using Analog System Lab Kit Pro board

This paper discusses modelling and parameters investigation of a photovoltaic array using Analog System Lab Kit Pro board offered by Texas Instrument for instructional laboratories on Electric and Electronic Engineering. The modelling of PV array is based on representation of the current-voltage characteristic by an analogue circuit developed using the components available on the Lab Kit board. The model is applicable for instructional laboratory investigation on the array current-voltage characteristic and its performance at maximum power point. This investigation expands the portfolio of the laboratory works available through Analog System Lab Kit Pro board

Real-time model of synchronous reluctance motor drive for laboratory based investigations

The Synchronous Reluctance Motor has received much attention in recent years as a very promising solution for electric drives in the near future. This paper presents a real-time model of the motor to be implemented into a software environment used for DSP control system development including debugging. The model is used in laboratory based investigations in academia in order to analyse the performance of electric drives based on a synchronous reluctance motor

Reduction of short circuit current using DC transmission and split-winding power transformer

This paper discusses a new scheme to reduce the level of fault currents in the feeder cable and power transformer windings under short-circuit conditions. The proposed scheme suggests splitting the feeder cable in two cables and connecting it to a network through two rectifier units. Therefore, the split windings of the power transformer are supplied by a six-conductor feeder using unidirectional dc current. Unidirectional magnetic flux produced by the windings are summarised in the transformer core resulting ac flux to ensure a normal transformer operation. The proposed scheme was analysed under short and open-circuit faults. It has been shown that the short-circuit currents in the cable conductors and transformer windings are reduced in 1.41 times in comparison to a conventional scheme