683 research outputs found

    Democracy without elections: 15 years of local democratic deficit in Nepal

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    It has been 14 years since local elections have been held in Nepal, and as a result democratisation at local level has stalled despite periodic national elections. Thanesh Bhusal explores why elections at local level have been suspended for so long, the impact this has had on citizen participation and the prospects for the revival of local elections in the near future

    Long read: the transformation of Nepal’s local development policymaking structures

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    Nepal’s local development policymaking regime is undergoing a transformation in order to adjust to the recently established federalist structure in Nepal. Here Thaneshwar Bhusal (Civil Servant and Researcher, Nepal) explains how local policymaking has adapted to the country’s new governance structures

    Additive Manufacturing of Biocompatible Thin Polymeric Tubular Structure

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    Additive manufacturing (AM) or 3D printing may be used to fabricate synthetic artery for use in, for example, coronary artery bypass surgery. Structurally, the artery comprises the intima layer and two other layers. Thus, we have suggested that a novel approach is to use different AM methods to fabricate the different parts of the artery and to devise a way to suitably join them. In the present work, we concentrated on the fabrication of a thin polymeric tubular structure that would mimic the intima. None of three in-house AM machines produced such a structure with the requisite thickness (0.074 mm). Thus, a novel device was designed to produce the aforementioned structure from a polymer solution. The combination of 15% polymer solution and rotational speed of the collector rod (a device part) of either 50 rpm or 75 rpm produced a structure with the requisite thickness and acceptable tensile properties

    Genre Awareness In The Writing Center

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    The Combined Effect of Photovoltaic and Electric Vehicle Penetration on Conservation Voltage Reduction in Distribution System

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    Global conditions over the past dozen years have led to an expanded appetite for renewable energy sources: The diminishing fossil fuel supply, the political instability of countries producing these fossil fuels, the ever-more destructive effects of global warming, and the lowering of costs for renewable energy technologies have made countries around the world reconsider their sources of energy. The proliferation of photovoltaic (PV) systems especially has surged dramatically with the decreasing initial costs for installation, and increasing government support in the form of renewable energy portfolios, feed-in-tariffs, tax incentives, etc. Furthermore, electric vehicles (EV) are also becoming widespread due to recent advances in battery and electric drive technologies, and the desperate need to reduce air pollution in urban areas. Meanwhile, electric utilities are always making an effort to run their system more efficiently by encouraging the use of energy-efficient appliances and customer participation in demand-side management programs. In an attempt to further reduce load demand; many utilities regulate the voltage along their distribution feeders in a particular way that is referred to as conservation voltage reduction (CVR). The key principle of CVR operation is that the ANSI standard voltage band between 114 and 126 volts can be compressed via regulation to the lower half (114–120) instead of the upper half (120–126), producing measurable energy savings at low cost and without harm to consumer appliances. As the penetration of distributed PV and EV charging station increases, this can dramatically change the conventional demand profile as PV system act as negative loads during the daylight hours, and EVs significantly increase load demand during charging. Consequently, traditional means of controlling the voltage by capacitor switching and voltage regulators can be improved in this “smart” grid era by adding a fleet of enabling devices including the smart PV inverter functionalities, such as Volt/VAR control, and intelligent EV charging schemes. This thesis explores how better energy conservation is achieved by CVR in a modern distribution system with advanced distributed PV systems inverters and EV loads. Then it summarizes computer simulations that are conducted on the IEEE 37 and IEEE 123 node test feeders using OpenDSS interfaced with MATLAB

    EVALUATING THE PERFORMANCE OF PROCESS-BASED AND MACHINE LEARNING MODELS FOR RAINFALL-RUNOFF SIMULATION WITH APPLICATION OF SATELLITE AND RADAR PRECIPITATION PRODUCTS

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    Hydrology Modeling using HEC-HMS (Hydrological Engineering Centre-Hydrologic Modeling System) is accepted globally for event-based or continuous simulation of the rainfall-runoff operation. Similarly, Machine learning is a fast-growing discipline that offers numerous alternatives suitable for hydrology research\u27s high demands and limitations. Conventional and process-based models such as HEC-HMS are typically created at specific spatiotemporal scales and do not easily fit the diversified and complex input parameters. Therefore, in this research, the effectiveness of Random Forest, a machine learning model, was compared with HEC-HMS for the rainfall-runoff process. In addition, Point gauge observations have historically been the primary source of the necessary rainfall data for hydrologic models. However, point gauge observation does not provide accurate information on rainfall\u27s spatial and temporal variability, which is vital for hydrological models. Therefore, this study also evaluates the performance of satellite and radar precipitation products for hydrological analysis. The results revealed that integrated Machine Learning and physical-based model could provide more confidence in rainfall-runoff and flood depth prediction. Similarly, the study revealed that radar data performance was superior to the gauging station\u27s rainfall data for the hydrologic analysis in large watersheds. The discussions in this research will encourage researchers and system managers to improve current rainfall-runoff simulation models by application of Machine learning and radar rainfall data

    Bridging Machine Learning for Smart Grid Applications

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    This dissertation proposes to develop, leverage, and apply machine learning algorithms on various smart grid applications including state estimation, false data injection attack detection, and reliability evaluation. The dissertation is divided into four parts as follows.. Part I: Power system state estimation (PSSE). The PSSE is commonly formulated as a weighted least-square (WLS) algorithm and solved using iterative methods such as Gauss-Newton methods. However, iterative methods have become more sensitive to system operating conditions than ever before due to the deployment of intermittent renewable energy sources, zero-emission technologies (e.g., electric vehicles), and demand response programs. Efficient approaches for PSSE are required to avoid pitfalls of the WLS-based PSSE computations for accurate prediction of operating conditions. The first part of this dissertation develops a data-driven real-time PSSE using a deep ensemble learning algorithm. In the proposed approach, the ensemble learning setup is formulated with dense residual neural networks as base-learners and a multivariate-linear regressor as a meta-learner. Historical measurements and states are utilized to train and test the model. The trained model can be used in real-time to estimate power system states (voltage magnitudes and phase angles) using real-time measurements. Most of current data-driven PSSE methods assume the availability of a complete set of measurements, which may not be the case in real power system data acquisition. This work adopts multivariate linear regression to forecast system states for instants of missing measurements to assist the proposed PSSE technique. Case studies are performed on various IEEE standard benchmark systems to validate the proposed approach. Part II: Cyber-attacks on Voltage Regulation. Several wired and wireless advanced communication technologies have been used for coordinated voltage regulation schemes in distribution systems. These technologies have been employed to both receive voltage measurements from field sensors and transmit control settings to voltage regulating devices (VRDs). Communication networks for voltage regulation can be susceptible to data falsification attacks, which can lead to voltage instability. In this context, an attacker can alter multiple field measurements in a coordinated manner to disturb voltage control algorithms. The second part of this dissertation develops a machine learning-based two-stage approach to detect, locate, and distinguish coordinated data falsification attacks on control systems of coordinated voltage regulation schemes in distribution systems with distributed generators. In the first stage (regression), historical voltage measurements along with current meteorological data (solar irradiance and ambient temperature) are provided to random forest regressor to forecast voltage magnitudes of a given current state. In the second stage, a logistic regression compares the forecasted voltage with the measured voltage (used to set VRDs) to detect, locate, and distinguish coordinated data falsification attacks in real-time. The proposed approach is validated through several case studies on a 240-node real distribution system (based in the USA) and the standard IEEE 123-node benchmark distribution system.Part III: Cyber-attacks on Distributed Generators. Part III of the dissertation proposes a deep learning-based multi-label classification approach to detect coordinated and simultaneously launched data falsification attacks on a large number of distributed generators (DGs). The proposed approach is developed to detect power output manipulation and falsification attacks on DGs including additive attacks, deductive attacks, and combination of additive and deductive attacks (attackers use the combination of additive and deductive attacks to camouflage their attacks). The proposed approach is demonstrated on several systems including the 240-node and IEEE 123-node distribution test system. Part IV: Composite System Reliability Evaluation. Traditional composite system reliability evaluation is computationally demanding and may become inapplicable to large integrated power grids due to the requirements of repetitively solving optimal power flow (OPF) for a large number of system states. Machine learning-based approaches have been used to avoid solving OPF in composite system reliability evaluation except in the training stage. However, current approaches have been utilized only to classify system states into success and failure states (i.e., up or down). In other words, they can be used to evaluate power system probability and frequency reliability indices, but they cannot be used to evaluate power and energy reliability indices unless OPF is solved for each failure state to determine minimum load curtailments. In the fourth part of this dissertation, a convolutional neural network (CNN)-based regression approach is proposed to determine the minimum amount of load curtailments of sampled states without solving OPF. Unavoidable load curtailments due to failures are then used to evaluate power and energy indices (e.g., expected demand not supplied) as well as to evaluate the probability and frequency indices. The proposed approach is applied on several systems including the IEEE Reliability Test System and Saskatchewan Power Corporation in Canada
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