ABSTRACT
Recently, we have reported the influence of various reaction atmospheres on the solid-state reaction kinetics of ferrocene, where oxalic acid dihydrate was used as a coprecursor. In this light, present study discusses on the nature of decomposed materials of the solid-state reactions of ferrocene in O2, air, and N2 atmospheres. The ambient and oxidative atmospheres caused the decomposition to yield pure hematite nanomaterials, whereas cementite nanomaterials along with α-Fe were obtained in N2 atmosphere. The obtained materials were mostly agglomerated. Elemental composition of each material was estimated. Using the absorbance data, the energy band gap values were estimated and the related electronic transitions from the observed absorption spectra were explored. Urbach energy was calculated for hematite, which described the role of defects in the decomposed materials. The nanostructures exhibited photoluminescence due to self-trapped states linked to their optical characteristics. Raman spectroscopy of hematite detected seven Raman modes, confirming the rhombohedral structure, whereas the D and G bands were visible in the Raman spectra for cementite. Thus, the reaction atmosphere significantly influenced the thermal decomposition of ferrocene and controls the type of nanomaterials obtained. Plausible reactions of the undergoing solid-state decomposition have been proposed.
ABSTRACT
The regenerative braking in the tram allows the energy to be returned to the power grid through a power inverter. Since the inverter location between the tram and the power grid is not fixed, resulting in a wide variety of impedance networks at grid coupling points, posing a severe threat to the stable operation of the grid-tied inverter (GTI). By independently changing the loop characteristics of the GTI, the adaptive fuzzy PI controller (AFPIC) can adjust according to different impedance network parameters. It is challenging to fulfill the stability margin requirements of GTI under high network impedance since the PI controller has phase lag characteristics. A correction method of series virtual impedance is proposed, which connects the inductive link in a series configuration with the inverter output impedance, correcting the inverter equivalent output impedance from resistance-capacitance to resistance-inductance and improving the system stability margin. Feedforward control is adopted to improve the system's gain in the low-frequency band. Finally, the specific series impedance parameters are obtained by determining the maximum network impedance and setting the minimum phase margin of 45°. The realization of virtual impedance is simulated by conversion to an equivalent control block diagram, and the effectiveness and feasibility of the proposed method are verified by simulation and a 1 kW experimental prototype.
ABSTRACT
An automotive supply chain includes a range of activities from the concept of the product to its final transfer to a customer and subsequent vehicle maintenance. The three distinct stages of this chain are production, sales, and maintenance. In many countries, automobile records are not available to the public and anyone who has access to the central database or government systems can tamper with these records. In addition, used vehicle maintenance and transfer histories remain unavailable or inaccessible. These issues can be overcome by incorporating state-of-the-art blockchain technology into automotive supply chain management. Blockchain technology uses a chain of blocks for distributed transfer and storage of information, creating a decentralized data register that makes records of any digital asset tamper-proof and transparent. In this paper, we implement a permissioned blockchain-based framework for secure and efficient supply chain management of the automobile industry. We employed Hyperledger Fabric; an enterprise-grade distributed ledger platform for developing solutions. In our solution, the blockchain is customized and private in order to ensure system security. We evaluated our system in terms of memory cost, monetary cost, and speed of execution. Our results demonstrate that only 346 MB of extra memory space is required for storing the automotive data of 1 million users, thus rendering the memory cost negligible. The monetary cost is insignificant as all open source blockchain resources are employed, and the speed of record update is also fast. Our results also show that the decentralization of the automotive supply chain using blockchain can implement system security with minor modifications in the established configuration of the web application database.
ABSTRACT
This paper examines the design and analysis of DC-DC converters for high-power and low-voltage applications such as renewable energy sources (RESs) and comparisons between converters based on switch stresses and efficiency. The RESs including photovoltaic arrays and fuel cell stacks must have enhanced output voltages, such as 380 V DC in the case of a full bridge inverter or 760 V DC in the case of a half bridge inverter, in order to interface with the 220 V AC grid-connected power system. One of the primary difficulties in developing renewable energy systems is enhancing DC-DC converters' efficiency to enable high step-up voltage conversion with high efficiency and low voltage stress. In the present work, the efficiency, current, and voltage stress of switches of an isolated Flyback boost converter, simple DC-DC Boost converter, and an Interleaved boost converter, are explored and studied relatively. The most suitable and optimized options with a high efficiency and low switching stress are investigated. The more suitable topology is designed and analyzed for the switch technology based on the Silicon-Metal Oxide Semiconductor Field Effect Transistor (Si-MOSFET) and the Gallium Nitride-High Electron Mobility Transistor (GaN-HEMT). The Analytical approach is analyzed in this paper based on efficiency and switching stress. It is explored that GaN HEMT based Flyback boost converter is the best. Finally, the future direction for further improving the efficiency of the proposed boost converter is investigated.
ABSTRACT
The growth of distributed generation significantly reduces the synchronous generators' overall rotational inertia, causing large frequency deviation and leading to an unstable grid. Adding virtual rotational inertia using virtual synchronous generators (VSG) is a promising technique to stabilize grid frequency. Due to coupled nature of frequency and active output power in a grid-tied virtual synchronous generator (GTVSG), the simultaneous design of transient response and steady state error becomes challenging. This paper presents a duplex PD inertial damping control (DPDIDC) technique to provide active power control decoupling in GTVSG. The power verses frequency characteristics of GTVSG is analyzed emphasizing the inconsistencies between the steady-state error and transient characteristics of active output power. The two PD controllers are placed in series with the generator's inertia forward channel and feedback channel. Finally, the performance superiority of the developed control scheme is validated using a simulation based study.
