352 research outputs found
Development of a Generic Model for Real-time Simulation and Assessment of the Dynamic Performance of a Large Scale Offshore Transmission Network
No full textThe Paris Agreement, which calls for countries to channel their efforts to limit global warming would require the deployment of large scale offshore wind energy in the North Sea. This includes the possibility of developing offshore infrastructure for deploying offshore wind power generation with installed capacity ranging from 70 to 150 GW by 2040 and increasing up to 180 GW by 2045. Presently, the Voltage Source Converter (VSC) based - High Voltage Direct Current (HVDC) transmission is considered the most suitable for transfer of offshore wind power from distant offshore wind farms (OWFs) to the onshore system. Amidst the available VSC topologies, Modular Multi-level Converter (MMC) topology is the most appropriate solution for the transfer of offshore wind power to onshore systems due to their enhanced performance during offshore and onshore disturbances. However, the currently deployed state-of-the-art MMC-HVDC transmission has a maximum capacity of 1.2 GW. Compatibility of this available technology for complex systems, with the working of parallel units contributing to the increase in power transfer capacity is still unknown. Hence, this demands the development and analysis of a generic model with parallel operation of MMC-HVDC transmission systems to transfer the bulk amount of power from large scale OWFs. Additionally, the implementation of large scale offshore networks leads to an increase in the penetration of power electronic (PE) converters in the electrical power system. The increase in PE converters causes technical challenges (e.g. due to unprecedented fast dynamic phenomena) related to voltage and frequency stability, and power flow coordination in the power system. In OWFs, the currently available current injection-based voltage control for PE converters are not suitable for voltage control in large scale PE dominated systems due to the absence of continuous voltage control and ineffectiveness during islanding. Moreover, in such power systems, the conventional controllers are not suitable for frequency control due to the absence of dynamic frequency control. Therefore, better control strategies are required in large scale offshore networks to enhance the dynamic characteristics of the power system. Conventionally, the OWFs are coupled to an AC collector platform through 33 kV High Voltage Alternating Current (HVAC) cables. The voltage is stepped-up to 145 kV at the collector platform, and power is transferred to the offshore converter station using 145 kV HVAC cables. However, in the upcoming projects, the rated voltage levels are expected to increase from 33 kV to 66 kV to avoid the use of such a collector platform and directly transfer power from OWFs to the offshore converter station using 66 kV HVAC cables. Hence, it would be better to understand the performance of large scale offshore networks developed with 66 kV voltage rating. This thesis proposes a digital twin model of a 2 GW offshore network with the parallel operation of two MMC-HVDC transmission links connecting four OWFs to two onshore systems representing a large scale power system. The MMCs are connected to a common bus on the AC side of the network, with one MMC creating the voltage reference for the common bus and the other MMC following this reference. Additionally, to mitigate the challenges corresponding to voltage and frequency stability in large scale offshore networks, a Direct Voltage Control (DVC) strategy is implemented in the Type-4 Wind Generators (WGs) representing the OWFs. After analyzing the need for 66 kV HVAC transmission from the OWFs to the offshore converter stations, a 66 kV offshore network is developed to achieve 2 GW offshore wind power transfer. The electrical power system is developed in the power system simulation software, RSCAD Version 5.011.1, in order to perform Electro-Magnetic Transient (EMT) based simulations. Initially, a single OWF with DVC implemented in the WG connected to an AC equivalent system is modelled to test the performance of DVC in a digital twin of a 66 kV HVAC network. The DVC provides continuous voltage control that improves the dynamic performance of the power system. As mentioned in most of the grid codes, the important requirement of reactive power injection by the OWF during dynamic conditions is satisfied by the controller. DVC also avoids the need for an external controller to perform such an action. To validate the working of the implemented DVC in RSCAD, a similar 66 kV HVAC network with the benchmark DVC model is developed in DIgSILENT PowerFactory 2019 SP2 (x64), for EMT simulations and tested under severe dynamic conditions. Both the models provide similar results, confirming the validation of the RSCAD model. Moreover, the RSCAD model provides a better representation of the real-world operation. To achieve the overall goal of developing a 2 GW offshore transmission network, a hybrid system with the hub-and-spoke principle is utilized in this thesis. The 2 GW offshore network is achieved by a modular approach, connecting four OWFs to a common bus, to which two MMCs are connected in parallel. The coordination between the implemented DVC in WGs and the control structures in MMCs is evaluated for different scenarios in the network. The performance of the 2 GW network in terms of short-term voltage stability and power flow during severe dynamic conditions in the grid is analyzed. The two most severe dynamic conditions chosen for assessment are; the disconnection of one OWF, and a three-phase fault in the middle of an HVAC cable. In the analysis, it is observed that even after the loss of generation from one OWF, the voltage at Point of Common Coupling (PCC) of other OWFs remains stable within the tolerance limit of 10 \%. Additionally, the loss of generation decreases the active power flow in MMC-1 since it is the one that creates the voltage reference. The power flow in MMC-2 is maintained with the corresponding active power reference. For the event of a three-phase fault, the OWF is islanded by the operation of a circuit breaker. During this event, with implemented DVC, the important requirement of reactive power injection from the islanded OWF as stated in most of the grid codes is achieved. This leads to the conclusion that the voltage control in MMC-1 provides the voltage reference in the network during the pre-fault and post fault conditions. However, DVC implemented in the WGs of OWFs take up the role of providing the voltage reference at corresponding PCCs when the OWFs are islanded from the network during the time of the fault.Electrical Engineering | Electrical Power Engineerin
"More Societal than Generational": Examining the Construction and Resistance of Generational Messages in the Workplace
No full textAuthor email: [email protected] Millennial generation, those born between 1980-2000, have drawn vast, sometimes fanatical, criticism in popular media. Slated as narcissistic praise hounds, they are cast as demanding graduate divas who are about to attack the workplace and everything ‘you hold sacred’ (Clark, 2008; Safer, 2007). The abundance of such messages about this generation in formats ‘tailored, targeted, and consumed’ by the public is problematic given that generational constructs are by many perceived as sacrosanct (Myers et al, 2010).
The proliferation of such criticism is by no means innocuous given the very likely impact that they will have on Millennial work opportunities. For many scholars the field of Millennial research suffers from a lack of empirical and cross sectional data to establish more calculated and careful generational constructs, – instead relying on or reacting to popular negative stereotypes. While some Millennial scholarship has begun to move beyond criticisms of popular media, Millennial research is by many considered contradictory at best and confusing at worst (Kowske et al, 2010). Additional difficulties arise when the scramble to publish more research-based work has led to methodologies which are inherently flawed because they reinforce the very same monolithic generational categories they are supposed to assess.
This study, undertaken in New Zealand, explores critical approaches as a means of examining the construction of generational messages and the establishment of generational difference. As a starting point, this small-scale examination analyses the very way in which generational messages are constructed and resisted within the workplace through an analysis of interviews undertaken with 26 employees of a Small to Medium Enterprise (SME) in the information technology sector.
Unlike many generational studies, this project did not seek to draw conclusions by framing differences and measuring responses across generational lines, but rather took a bottom-up approach to understand how participants themselves constructed and resisted messages about generational difference. The project asked two research questions: First, how are generational messages constructed in the context of the workplace? And second, how are generational messages resisted in the workplace? Through axial coding this research categorized five themes under which participants constructed generational difference. These five themes are Technology, Voice, Fairness, Informality, and Stimulus. Broadly speaking, these themes were underpinned by a belief that Millennials have a great demand for respect, democratic process, and the reduction of power distances.
Given the critical approach, the study also observed resistance as a component of the discursive process. As such this research outlines the partiality of resistance and outlines strategies of resistance employed by employees. In line with the idea that construction and resistance are mutually implicated as negotiation, participants were frequently observed simultaneously constructing and resisting generational difference, both synchronically and diachronically. Through axial coding this study also categorized three strategies of resistance. These three strategies are established as Dismissal, the Third Person Effect, and the Decline Metaphor.
This research highlights the usefulness of adopting critical approaches by illustrating the way in which generational meaning is perpetually produced, reproduced, negotiated, and resisted by participants (Murphy, 1998). While there are several factors which are indicative of the Millennial generation, this thesis establishes the hegemonic character of most constructions of generational difference. Given the fragmented and complex state of society, this thesis posits that the usefulness of the monolithic birth-cohort generation has long since passed and we should instead look to understanding generations in terms of their consumption of similar cultural capital
Journal Of The Nepal Medical Association
No full textNEW DIRECTOR
NEPAL MEDICAL COUNCIL
CONFERENCE AND SEMINARS
SYMPOSIUM
MEDICLA NEWS
BIRTHDAY AWARDS
CENTRAL BODY
KATHMANDU BRANCH
BIRATNAGAR BRANCH
AN ACKNOWLEDGEMENT
JORE GANESH PRESS Pvt. Ltd
Influence of geometric parameters on 3D periodic lattice effective properties
No full textLattice materials are generated by tessellating a unit cell, composed of a specific truss configurations, in an infinite periodicity to combine the effect of bulk material properties and geometric periodicity. They offer enhanced mechanical and dynamic properties per unit mass, and the ability to engineer the material response by optimizing the unit cell. Characterizing lattice properties through experiments can be a time consuming and costly process, so analytical and numerical methods are crucial. Specifically, the Bloch-wave homogenization approach allows one to characterize the effective static properties of the lattice unit cell while simultaneously analyzing wave propagation properties. While this analysis has been used for some time, a thorough study of this approach on 3D lattice materials with different symmetries and geometries is presented here. Using Bloch-wave homogenization, multiple periodic lattices with cubic, transversely isotropic, and tetragonal symmetry, including an auxetic geometry, over a wide range of relative densities are analyzed within a finite element framework. The effect of geometric parameters on lattice properties is discussed and a comparison between lattices based on their anisotropy index is presented. Method studied in this thesis can be extended for designing multifunctional metamaterials with optimized static and dynamic properties simultaneously. This work can also serve as the basis for nondestructive evaluation of metamaterials properties using ultrasonic velocity measurements.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2021-05-01The student, Ganesh Patil, accepted the attached license on 2019-04-24 at 19:00.The student, Ganesh Patil, submitted this Thesis for approval on 2019-04-24 at 19:11.This Thesis was approved for publication on 2019-04-25 at 12:03.DSpace SAF Submission Ingestion Package generated from Vireo submission #13897 on 2019-08-22 at 15:08:33Made available in DSpace on 2019-08-23T20:36:11Z (GMT). No. of bitstreams: 2
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A learning hierarchy for classification and regression
No full textThesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 51-53).This thesis explores the problems of learning analysis of variance (ANOVA) decompositions over GF(2) and R, as well as a general regression setup. For the problem of learning ANOVA decompositions, we obtain fundamental limits in the case of GF(2) under both sparsity and degree structures. We show how the degree or sparsity level is a useful measure of the complexity of such models, and in particular how the statistical complexity ranges from linear to exponential in the dimension, thus forming a "learning hierarchy". Furthermore, we discuss the problem in both an "adaptive" as well as a "one-shot" setting, where in the adaptive case query choice can depend on the entire past history. Somewhat surprisingly, we show that the "adaptive" setting does not yield significant statistical gains. In the case of R, under query access, we demonstrate an approach that achieves a similar hierarchy of complexity with respect to the dimension. For the general regression setting, we outline a viewpoint that captures a variety of popular methods based on locality and partitioning of some kind. We demonstrate how "data independent" partitioning may still yield statistically consistent estimators, and illustrate this by a lattice based partitioning approach.by Ganesh Ajjanagadde.M. Eng
V.S. Naipaul’s ?The Mystic Masseur?: A Study of Post- Colonial Myth and Reality
No full text<h3 data-fontsize="17" data-lineheight="23">Abstract</h3>
<p>The Mystic Masseur is one of the V.S. Naipaul’s finest comic creations in which we see immense sensibility, humour, success, politics and endless inventive imagination that have become the hallmarks of the author’s genius. It is Naipaul’s first novel that depicts the story of the rise of Ganesh Ramsumair, from failed primary teacher and struggling masseur to author, revered mystic and M.B.E. It is a journey memorable for its hilarious and bewildering success through politics. V.S. Naipaul has made the claim that the story of Ganesh Ramsumair is the history of their time. In each step of the career of Ganesh Ramsumair the author has satirized the rise of power of a representative of the country, called Trinidad which was about to achieve it’s independence from the British colonial rule in 1962.Beneath the muchness and manyness the author traces the romance and realism, imagination and fact of the ?rise? and ?decline? of Ganesh Ramsumair. The story of the novel is not only the life history of Ganesh Ramsumair; rather it is a story of social and economic life of the Indian islanders. The author shows his alienation and rootlessness of the people migrated from India to Trinidad. Here he puts stress on the importance of imagination for survivalThe question is whether the novel The Mystic Masseur depicts the real Trinidad, the question is answered in King’s observations in his book. ?Those familiar with Trinidadian history should recognize how Naipaul has used local events, characters and such politicians characters and such politicians as Uriah Butler, Albert Gomes, Arthur Cipriani and Naipaul’s two uncles, Rudranath and SimbhoonathCapildeo in his novel. Naipaul’s early fiction is based on memories of Trinidadian cultural and political life before he left for England in 1950.? (King 29) My paper proposes to examine how V.S. Naipaul usesthe post-colonial myth and reality in his novel The Mystic Masseu</p>
Analysis of substation energy using Conservation Voltage Reduction in distribution system
No full textCD16a with oligomannose-type N-glycans is the only “low-affinity” Fc γ receptor that binds the IgG crystallizable fragment with high affinity in vitro
No full textFc γ receptors (FcγRs) bind circulating IgG (IgG1) at the surface of leukocytes. Antibodies clustered at the surface of a targeted particle trigger a protective immune response through activating FcγRs. Three recent reports indicate that the composition of the asparagine-linked carbohydrate chains (N-glycans) of FcγRIIIa/CD16a impacted IgG1-binding affinity. Here we determined how N-glycan composition affected the affinity of the “low-affinity” FcγRs for six homogeneous IgG1 Fc N-glycoforms (G0, G0F, G2, G2F, A2G2, and A2G2F). Surprisingly, CD16a with oligomannose N-glycans bound to IgG1 Fc (A2G2) with a KD = 1.0 ± 0.1 nM. This affinity represents a 51-fold increase over the affinity measured for CD16a with complex-type N-glycans (51 ± 8 nM) and is comparable with the affinity of FcγRI/CD64, the sole “high-affinity” FcγR. CD16a N-glycan composition accounted for increases in binding affinity for the other IgG1 Fc glycoforms tested (10–50-fold). This remarkable sensitivity could only be eliminated by preventing glycosylation at Asn162 with an Asn-to-Gln mutation; mutations at the four other N-glycosylation sites preserved tighter binding in the Man5 glycoform. None of the other low-affinity FcγRs showed more than a 3.1-fold increase upon modifying the receptor N-glycan composition, including CD16b, which differs from CD16a by only four amino acid residues. This result indicates that CD16a is unique among the low-affinity FcγRs, and modifying only the glycan composition of both the IgG1 Fc ligand and receptor provides a 400-fold range in affinities.This research was originally published in the Journal of Biological Chemistry. Subedi, Ganesh P., and Adam W. Barb. "CD16a with oligomannose-type N-glycans is the only “low-affinity” Fc γ receptor that binds the IgG crystallizable fragment with high affinity in vitro." Journal of Biological Chemistry 293, no. 43 (2018): 16842-16850. © the Author(s). doi: 10.1074/jbc.RA118.004998.</p
Revealing antiferromagnetic transition of van der Waals MnPS3 via vertical tunneling electrical resistance measurement
No full textUnderstanding the correlation between the electronic and magnetic properties of materials is a crucial step to functionalize or modulate their properties. However, it is not straightforward to electrically characterize magnetic insulators, especially large-bandgap materials, due to their high resistivity. Here, we successfully performed electrical measurements of a two-dimensional (2D) antiferromagnetic insulator, van der Waals-layered MnPS3, by accounting for the vertical graphene/MnPS3/graphene heterostructure. Antiferromagnetic transition is observed by the variance in electrical resistance from the paramagnetic to antiferromagnetic transition near similar to 78 K in the vertically stacked heterostructure devices, which is consistent with the magnetic moment measurement. This opens an opportunity for modulating the magnetic transition of 2D van der Waals materials via an electrical gate or surface functionalization. (c) 2019 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)11sciescopu
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