A paradigm shift in power systems is observed due to the massive integration of renewable energy sources (RESs) as distributed generators. Mainly, solar photovoltaic (PV) panels and wind generators are extensively integrated with the modern power system to facilitate green efforts in the electrical energy sector. However, integrating these RESs destabilizes the frequency of the modern power system. Hitherto, the frequency control has not drawn sufficient attention due to the reduced inertia and complex control of power electronic converters associated with renewable energy conversion systems. Thus, this article provides a critical summary on the frequency control of solar PV and wind-integrated systems. The frequency control issues with advanced techniques, including inertia emulation, de-loading, and grid-forming, are summarized. Moreover, several cutting-edge devices in frequency control are outlined. The advantages and disadvantages of different approaches to control the frequency of high-level RESs integrated systems are well documented. The possible improvements of existing approaches are outlined. The key research areas are identified, and future research directions are mentioned so that cutting-edge technologies can be adopted, making the review article unique compared to the existing reviews. The article could be an excellent foundation and guidance for industry personnel, researchers, and academicians.

This paper proposes a microcontroller based control method for the maximum power point tracking (MPPT) of a photovoltaic system under variable temperature and insolation conditions. For the reduction of tracking time, fuzzy logic control algorithm is implemented with the embedded microcontroller for improved performance as compared to conventional techniques in power efficiency and swift maximum power point tracking. The system includes a photovoltaic array, a PWM controlled DC-DC converter and sensor circuits. The designed controller regulates the converter output voltage by varying duty cycle of the PWM signal using maximum power point (MPP) algorithm and it maximizes the output power extracted from photovoltaic array. This paper discusses the low cost implementation of MPP algorithm in a 8-bit microcontroller using the tools and techniques to generate optimized real time code in C for ATMega8 microcontroller which will demonstrate how maximum power point tracker might provide elegant and efficient solution for increasing the efficiency of a solar system based on experimental results rather than on mathematical models. Keywords-Maximum power point tracking (MPPT), photovoltaic (PV), fuzzy logic control (FLC), boost DC-DC converter, microcontroller.

A longstanding goal of spintronics is to inject, then coherently transport, and finally detect electron spins in a semiconductor nanowire in which a single quantized subband is occupied by the electrons at room temperature. Here, the achieving of this goal in electrochemically self-assembled 50-nm diameter InSb nanowires is reported and substantiated by demonstrating both the spin-valve effect and the Hanle effect. Observing both effects in the same sample allows one to estimate the electron mobility and the spin relaxation time in the nanowires. It is found that despite four orders of magnitude degradation in the mobility compared to bulk or quantum wells and a resulting four orders of magnitude increase in the Elliott-Yafet spin relaxation rate, the spin relaxation time in the nanowires is still about an order of magnitude longer than what has been reported in bulk and quantum wells. This is caused by the elimination or suppression of the D'yakonov-Perel' spin relaxation through single subband occupancy. These experiments shed light on the nature of spin transport in a true quantum wire and raise hopes for the realization of a room-temperature Datta-Das spin transistor, where single subband occupancy is critical for optimum performance.

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Bangladesh, a lower-middle-income country in South Asia and expected to be a developing country by 2024, is one of the most densely populated countries in the world, with 166.30 million (WDI, 2021) people. Foreign Aid (FA) plays a vital role in the economic development of Bangladesh. Foreign Aid, loans, and grants generally, which we call Official Development Assistance (ODA) (in this study, we have used the term 'Foreign aid') have increased gradually over the years after the liberation of Bangladesh with the increase of per capita GDP. In our study, we have conducted a single country investigation on Bangladesh and examined the impact of Foreign Aid on the Economic growth of Bangladesh from 1971 to 2019. The ARDL bounds test methodology was applied in the study, followed by the unit root test and the bound test for cointegration. Several diagnostic tests were conducted to check the stability and reliability of the model. The obtained results revealed that Foreign Aid has a significant and positive impact on the Economic growth of Bangladesh in the long- and short-run. The coefficients of the variables of our study refer that a 1(one) unit increase in foreign Aid would intensify 0.24 units of Economic growth in Bangladesh. In line with Foreign Aid, Gross capital formation also has a significant positive impact on the country's economic development. On the contrary, trade openness has a negative but insignificant impact both in the short and long run. Besides, population growth negatively and significantly impacts economic growth in the long run. In this study, finally, we have recommended some policy implications for the Government of Bangladesh.