Load-Balancing Strategies in Discrete Element Method Simulations

In this research, we investigate the influence of a load-balancing strategy and parametrization on the speed-up of discrete element method simulations using Lethe-DEM. Lethe-DEM is an open-source DEM code which uses a cell-based load-balancing strategy. We compare the computational performance of different cell-weighing strategies based on the number of particles per cell (linear and quadratic). We observe two minimums for particle to cell weights (at 3, 40 for quadratic, and 15, 50 for linear) in both linear and quadratic strategies. The first and second minimums are attributed to the suitable distribution of cell-based and particle-based functions, respectively. We use four benchmark simulations (packing, rotating drum, silo, and V blender) to investigate the computational performances of different load-balancing schemes (namely, single-step, frequent and dynamic). These benchmarks are chosen to demonstrate different scenarios that may occur in a DEM simulation. In a large-scale rotating drum simulation, which shows the systems in which particles occupy a constant region after reaching steady-state, single-step load-balancing shows the best performance. In a silo and V blender, where particles move in one direction or have a reciprocating motion, frequent and dynamic schemes are preferred. We propose an automatic load-balancing scheme (dynamic) that finds the best load-balancing steps according to the imbalance of computational load between the processes. Furthermore, we show the high computational performance of Lethe-DEM in the simulation of the packing of 108 particles on 4800 processes. We show that simulations with optimum load-balancing need ≈40% less time compared to the simulations with no load-balancing.

PERFORMANCE EVALUATION OF VOLTAGE RECTIFIERS FOR ENERGY HARVESTING APPLICATIONS

Voltage multipliers are used to convert the low AC voltage output of energy harvesters into relatively high DC voltage for portable devices and wireless sensor nodes (WSNs) applications. DC voltage conversion is required to operate an electronic device or recharge battery. In order, to convert the low AC voltage output of the energy harvester into relatively high DC voltage, a voltage multiplier circuit need to be integrated with the energy harvester. In this study, a Prototype-1 (two-stages) and Prototype-2 (three-stage) Dickson voltage multipliers and Prototype-3 (seven-stage) Cockcroft-Walton voltage multiplier circuits are developed. The device is capable of converting a low voltage of 50 mV into 350 mV. The research focuses on the development and characterization of Prototype-1, Prototype-2 and Prototype-3 circuits. Results indicate that the determination of load resistance is important for better output power. The maximum power of 11.97 μW was obtained by prototype-3 elucidating better power compared to prototype-1 and prototype-2 and the power was obtained at an optimum load of 560 kΩ. Furthermore, a rectenna tested at different distances from the source, revealed that a prototype-2 produced a maximum power of 3.01 × 10 -6 μW, at an optimum load of 560 kΩ.

ANALISA PENENTUAN SILINDER HIDROLIK PADA KONDISI OPTIMUM PINTU PENGURAS KOLAM PASIR PLTA BATANG AGAM

The Batang Agam Hydroelectric Power Plant is a run of river type plant that has water purification stages before being used to turn a turbine generator. One of them is a sand pool that functions to deposit sand, mud and impurities carried by river water, where the drainage condition is currently experiencing some damage so it needs to be developed in the hoisting system of the fixed valve drain using a hydraulic lifting system and this requires initial analysis in the form of fixed valve loading at optimum conditions which then becomes the basis for determining the hydraulic cylinder.The research methodology in this writing includes field observations accompanied by a literature review. With the data obtained, we then analyze the optimum load on the Batang Agam hydropower fixed valve drain to be a reference in planning hydraulic cylinders as a hoisting system for the Sand pool fixed valve drain.From this final project, it can be concluded that the optimum load of the Batang Agam fixed valve drain at an elevation of 684.5 meters above sea level of 10472.95 kg equivalent to 10 tons is a conditional situation in the rainy season, and a medium load at an elevation of 683.7 meters above sea level of 9039.04 kg equivalent to 9 tons, Based on the calculation of hydraulic cylinder power at the optimum load obtained Ø cylindrical tube 360 mm, medium load obtained Ø cylindrical tube 320 mm.

The practical power flow analysis program based on matlab GUI developed for educational purposes for students in smart grids: Oyamatlab

With the rapid development of today's technology, it has become possible to improve the electricity grid by using computer and network technologies in electricity networks. Thus, electricity grids will be able to provide sustainable, safe, and uninterrupted energy to consumers by allowing a two-way flow of information and electricity. Networks that can do this are called smart grids. Although conventional power lines have unidirectional power flow, a smart grid; enables the bidirectional flow of information and electricity by placing various hardware and software on the network. The main purpose of this study that tackles the smart grid is to introduce an educational program that can perform optimum load flow analysis based on Matlab GUI that can be used by undergraduate, graduate, and PhD students. Especially, students will be able to use the program easily in subjects related to loading flow analysis in electrical networks. Students using the program will have the opportunity to see different algorithm results in IEEE busbar systems and compare them with each other. The developed program realizes the optimum load distribution in bus systems accepted by IEEE in the smart grid using various metaheuristic algorithms and uses objective functions such as power losses, fuel cost, and voltage adjustment while performing optimum load distribution analysis. As a result of the program called Oyamatlab, optimum values in the selected busbar system are obtained. This is the program with a simple user interface for students to use without difficulty; it can perform optimum load distribution analysis by selecting different purpose functions.

Quasi Oppositional Dragonfly Algorithm for Load Balancing in Cloud Computing Environment

In Cloud Computing (CC), load balancing tasks remain an essential problem of spreading resources from a data center to ensure that each Virtual Machine (VM) has a balanced load to achieve maximum utilization of its capabilities. In the CC world, load balancing is a Non-Polynomial (NP) problem solved with metaheuristic algorithms. A new Quasi Oppositional Dragonfly Algorithm for Load Balancing (QODA-LB) was developed to achieve the optimal resource scheduling in a CC setting. The proposed QODA-LB algorithm uses three variables to compute an objective function: run time, running cost, and load. The QODA-LB algorithm assigns tasks to VM based on its potential and the derivative objective function. Also, the QODA-LB algorithm uses the principle of Quasi-Oppositional Based Learning (QOBL) to increase the standard Dragonfly Algorithm's (DA) convergence rate. A comprehensive series of experiments were conducted, and the findings were analyzed in a variety of ways to ensure the efficient performance increased by the QODA-LB algorithm. The simulation's results demonstrated optimum load balancing efficiency and outperformed the leading approaches.