First-principles study of MoS2_2 and MoSe2_2 nanoclusters in the framework of evolutionary algorithm and density functional theory

Evolutionary algorithm is combined with full-potential ab-initio calculations to investigate conformational space of (MoS$_2$)$_n$ and (MoSe$_2$)$_n$ (n=1-10) nanoclusters and to identify the lowest energy structural isomers of these systems. It is argued that within both BLYP and PBE functionals, these nanoclusters favor sandwiched planar configurations, similar to their ideal planar sheets. The second order difference in total energy ($\Delta_2$E) of the lowest energy isomers are computed to estimate the abundance of the clusters at different sizes and to determine the magic sizes of (MoS$_2$)$_n$ and (MoSe$_2$)$_n$ nanoclusters. In order to investigate the electronic properties of nanoclusters, their energy gap is calculated by several methods, including hybrid functionals (B3LYP and PBE0), GW approach, and $\Delta$scf method. At the end, the vibrational modes of the lowest lying isomers are calculated by using the force constants method and the IR active modes of the systems are identified. The vibrational spectra are used to calculate the Helmholtz free energy of the systems and then to investigate abundance of the nanoclusters at finite temperatures.Comment: 6 figures; 3 table

Design of a Single-Core Digital-to-Analog Converter with Ultra-Wideband and Low Power Consumption for CUWB-IR Applications

Data converters are intermediate circuits used to connect between two analog and digital ranges. Data converters are not only used for converting audio into a microphone or speaker, but also for converting audio into a camera or display, transferring information to a computer or digital signal processor. At these times, the need for data converters is not invested in every aspect of life. Digital to analog converters is a leading part of these converters, which are widely used in most audio and video circuits. In this thesis, we have proposed a 4-bit 1GS/s DAC for CUWB-IR usage. To enhance the above performance with superior speed and the need for linearity, every significant block containing the convenient sources, current switches, and deglitcher were designed optimally and a new DAC converter circuit was developed which improves the linearity. The designed DAC was performed using a commercial 130 nm CMOS process. DAC INL/DNL≤0.22LSB features more than high Nyquist bandwidth at extremely low power losses of 0.45 mW. The proposed DAC achieves the best FoMs at the right time for advanced DACs

Optimal Service Provisioning in IoT Fog-based Environment for QoS-aware Delay-sensitive Application

This paper addresses the escalating challenges posed by the ever-increasing data volume, velocity, and the demand for low-latency applications, driven by the proliferation of smart devices and Internet of Things (IoT) applications. To mitigate service delay and enhance Quality of Service (QoS), we introduce a hybrid optimization of Particle Swarm (PSO) and Chemical Reaction (CRO) to improve service delay in FogPlan, an offline framework that prioritizes QoS and enables dynamic fog service deployment. The method optimizes fog service allocation based on incoming traffic to each fog node, formulating it as an Integer Non-Linear Programming (INLP) problem, considering various service attributes and costs. Our proposed algorithm aims to minimize service delay and QoS degradation. The evaluation using real MAWI Working Group traffic data demonstrates a substantial 29.34% reduction in service delay, a 66.02% decrease in service costs, and a noteworthy 50.15% reduction in delay violations compared to the FogPlan framework