Browsing by Author "Kumar, Pankaj"
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- Chaos in Pulsed Laminar FlowKumar, Pankaj (Virginia Tech, 2010-08-09)Fluid mixing is a challenging problem in laminar flow systems. Chaotic advection can play an important role in enhancing mixing in such flow. In this thesis, different approaches are used to enhance fluid mixing in two laminar flow systems. In the first system, chaos is generated in a flow between two closely spaced parallel circular plates by pulsed operation of fluid extraction and reinjection through singularities in the domain. A singularity through which fluid is injected (or extracted) is called a source (or a sink). In a bounded domain, one source and one sink with equal strength operate together as a source-sink pair to conserve the fluid volume. Fluid flow between two closely spaced parallel plates is modeled as Hele-Shaw flow with the depth averaged velocity proportional to the gradient of the pressure. So, with the depth-averaged velocity, the flow between the parallel plates can effectively be modeled as two-dimensional potential flow. This thesis discusses pulsed source-sink systems with two source-sink pairs operating alternately to generate zig-zag trajectories of fluid particles in the domain. For reinjection purpose, fluid extracted through a sink-type singularity can either be relocated to a source-type one, or the same sink-type singularity can be activated as a source to reinject it without relocation. Relocation of fluid can be accomplished using either "first out first in" or "last out first in" scheme. Both relocation methods add delay to the pulse time of the system. This thesis analyzes mixing in pulsed source-sink systems both with and without fluid relocation. It is shown that a pulsed source-sink system with "first out first in" scheme generates comparatively complex fluid flow than pulsed source-sink systems with "last out first in" scheme. It is also shown that a pulsed source-sink system without fluid relocation can generate complex fluid flow. In the second system, mixing and transport is analyzed in a two-dimensional Stokes flow system. Appropriate periodic motions of three rods or periodic points in a two-dimensional flow are determined using the Thurston-Nielsen Classification Theorem (TNCT), which also predicts a lower bound on the complexity generated in the fluid flow. This thesis extends the TNCT -based framework by demonstrating that, in a perturbed system with no lower order fixed points, almost invariant sets are natural objects on which to apply the TNCT. In addition, a method is presented to compute line stretching by tracking appropriate motion of finite size rods. This method accounts for the effect of the rod size in computing the complexity generated in the fluid flow. The last section verifies the existence of almost invariant sets in a two-dimensional flow at finite Reynolds number. The almost invariant set structures move with appropriate periodic motion validating the application of the TNCT to predict a lower bound on the complexity generated in the fluid flow.
- How much does the firm's alliance network matter?Kumar, Pankaj; Liu, Xiaojin; Zaheer, Akbar (Wiley, 2022-01-10)Research Summary Extant empirical work partitioning the variance in firm (business segment) profitability has identified industry, corporate parent, business segment, and time as key sources. However, this variance decomposition research stream has treated firms as atomistic, autonomous entities. We employ a fast-unfolding community-detection algorithm to detect firms' network memberships and use the Shapley Value method to isolate the effect of the firm's alliance network, in addition to industry, corporate parent, business segment, and year effects, on the variance in business unit performance. Our findings demonstrate that the effect of the firm's alliance network explains 11% of the variance in firm ROA among 16,381 business segments from 1979 through 1996. We also extend the time period through 2018 and find that our results broadly hold. Managerial Summary In the search for superior firm performance, managers typically focus their attention externally on profitable industries in which to operate, as well as internally on their firms' idiosyncratic and valuable resources and capabilities. In addition to these profitability sources, our work suggests another important, but heretofore overlooked, factor in the managerial quest for competitive advantage: the value-creating potential of alliance networks. We employ a machine-learning algorithm to detect firms' network memberships. Our findings indicate that as much as 11% of the variance in firm profitability (ROA) is explained by the network of alliances of which the firm is a part. Our study also implies that the emphasis on networks continues to be relevant in a technology age in which industry boundaries are blurring.
- Mendelian inheritance of trimodal CpG methylation sites suggests distal cis-acting genetic effectsZaghlool, Shaza B.; Al-Shafai, Mashael; Al Muftah, Wadha A.; Kumar, Pankaj; Gieger, Christian; Waldenberger, Melanie; Falchi, Mario; Suhre, Karsten (2016-11-22)Background Environmentally influenced phenotypes, such as obesity and insulin resistance, can be transmitted over multiple generations. Epigenetic modifications, such as methylation of DNA cytosine-guanine (CpG) pairs, may be carriers of inherited information. At the population level, the methylation state of such “heritable” CpG sites is expected to follow a trimodal distribution, and their mode of inheritance should be Mendelian. Methods Using the Illumina Infinium 450 K DNA methylation array, we determined DNA CpG-methylation in blood cells from a family cohort 123 individuals of Arab ethnicity, including 18 elementary father-mother-child trios, we asked whether Mendelian inheritance of CpG methylation is observed, and most importantly, whether it is independent of any genetic signals. Using 40× whole genome sequencing, we therefore excluded all CpG sites with possibly confounding genetic variants (SNP) within the binding regions of the Illumina probes. Results We identified a total of 955 CpG sites that displayed a trimodal distribution and confirmed trimodality in a study of 1805 unrelated Caucasians. Of 955 CpG sites, 99.9% observed a strict Mendelian pattern of inheritance and had no SNP within +/−110 nucleotides of the CpG site by design. However, in 97% of these cases a distal cis-acting SNP within a +/−1 Mbp window was found that explained the observed CpG distribution, excluding the hypothesis of epigenetic inheritance for these clear-cut trimodal sites. Using power analysis, we showed that in 46% of all cases, the closest CpG-associated SNP was located more than 1000 bp from the CpG site. Conclusions Our findings suggest that CpG methylation is maintained over larger genomic distances. Furthermore, nearly half of the SNPs associated with these trimodal sites were also associated with the expression of nearby genes (P = 4.08 × 10−6), implying a regulatory effect of these trimodal CpG sites.
- Rethinking Directors' Effectiveness: The Development and Empirical Analysis of a Novel ModelCalvano da Silva, Felipe (Virginia Tech, 2022-04-01)The purpose of this dissertation is to introduce and empirically test a new theoretical perspective for assessing board effectiveness. Although the ability-motivation models provide a fruitful foundation in developing the characteristics that influence directors' job effectiveness, there are limitations this these models. First, the directors' ability and motivation dimensions are not clear, as existing conceptualizations are fungible and provide little clarity for theoretical and empirical research. Second, the ability-motivation models overlook several characteristics that are known to influence job performance but do not fit within the current dimensions. Finally, the current studies implicitly assume that all directors on the board have the same opportunity to monitor and advise in every domain. Therefore, I integrate the corporate governance literature on board effectiveness and the social psychology literature on job performance and propose that boards' effectiveness is a function of individual directors' capacity, engagement, and opportunity. This dissertation offers several contributions. First, I propose a theoretical model that illuminates and extends the core dimensions (i.e., capacity, engagement, and opportunity) of directors' effectiveness. The core dimensions of the model in my dissertation provide a much-needed conceptual clarity and coherence to the constructs that influence directors' effectiveness, which supports the development of stronger theory of directors' effectiveness. Second, by exploring the role of opportunity, I challenge one major assumption of the corporate governance field that all directors on the board have the same responsibility to monitor and advise in all domains. Third, the dissertation begins to shed light to the 'black box' of boards of directors by exploring how boards might enable directors to exert their full potential regarding their board functions.
- The signaling effect of supplier's customer network instability on service price: Insights from the container shipping charter marketKumar, Pankaj; Nowinska, Agnieszka; Schramm, Hans-Joachim (Wiley, 2023-04)In a service exchange setting, the supply management literature generally assumes, with notable exceptions, the availability of complete information regarding supplier reliability. Highlighting the information asymmetry in supplier evaluation and using signaling theory, we argue that for a focal buyer, a supplier's downstream ego-network instability, that is, other buyers' turnover in a supplier's network from one period to the next, acts as a signal of supplier unreliability, thereby reducing the price that the buyer pays to the supplier in a service exchange. Furthermore, we suggest that focal buyer-supplier relationship strength and structural equivalence weaken the negative effect of instability because the buyer has a more direct and positive experience with the supplier. Using a dataset of 3263 unique dyads formed by 260 buyers (shipoperators) and 493 suppliers (shipowners) during the 2000-2018 period in the container shipping charter market, we find support for our hypotheses, except for the contingent effect of structural equivalence. Our study contributes to signaling literature and network research by developing a supplier's downstream ego-network instability as a salient heuristic for a focal buyer's pricing decisions. These findings equip buyer managers who may not accurately foresee supplier service quality in the charter market with a new supplier evaluation tool: a supplier's downstream ego-network instability.
- Strategic ManagementKennedy, Reed; Jamison, Eli; Simpson, Joseph; Kumar, Pankaj; Kemp, Ayenda; Awate, Kiran; Manning, Kathleen (Pamplin College of Business in association with Virginia Tech Publishing, 2020-08)
Strategic Management (2020) is a 343-page open educational resource designed as an introduction to the key topics and themes of strategic management. The open textbook is intended for a senior capstone course in an undergraduate business program and suitable for a wide range of undergraduate business students including those majoring in marketing, management, business administration, accounting, finance, real estate, business information technology, and hospitality and tourism. The text presents examples of familiar companies and personalities to illustrate the different strategies used by today’s firms and how they go about implementing those strategies. It includes case studies, end of section key takeaways, exercises, and links to external videos, and an end-of-book glossary. The text is ideal for courses which focus on how organizations operate at the strategic level to be successful. Students will learn how to conduct case analyses, measure organizational performance, and conduct external and internal analyses. If you are an instructor reviewing, adopting, or adapting this textbook, please help us understand your use by filling out this form http://bit.ly/strategy-interest. How to access this book
This text is available in multiple formats including PDF, a low-resolution PDF which is faster to download, Open Document Format (ODT), and ePub found on the left side of your screen. It is also available online in Pressbooks at https://pressbooks.lib.vt.edu/strategicmanagement. Softcover print versions are available at the manufacturer's lowest price in color interior or black & white interior. The main landing page for this book is: https://doi.org/10.21061/strategicmanagement. Attribution
This textbook was adapted for use in Virginia Tech’s Pamplin College of Business capstone course, MGT 4394 Strategic Management, and is shared under a Creative Commons Attribution Non-Commercial ShareAlike 3.0 license. It is adapted without attribution to the original 2010 author or publisher at their request. It is adapted from Mastering Strategic Management which was published by the University of Minnesota Publishing in 2015 as an adaptation of the 2010 version. University of Minnesota Publishing reformatted the original text, and replaced some images and figures to make the resulting whole more shareable but did not otherwise significantly alter or update the original 2010 text. Instructor ancillaries
Powerpoint slides are available at http://hdl.handle.net/10919/102735. A test bank only for instructors is also available at http://hdl.handle.net/10919/104179. Find, adapt and share resources
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Chapter 1: Mastering Strategy: Art and Science
Chapter 2: Assessing Organizational Performance
Chapter 3: Evaluating the External Environment
Chapter 4: Evaluating the Internal Environment
Chapter 5: Synthesis of Strategic Issues and Analysis
Chapter 6: Selecting Business-Level Strategies
Chapter 7: Innovation Strategies
Chapter 8: Selecting Corporate-Level Strategies
Chapter 9: Competing in International Markets
Chapter 10: Executing Strategy through Organizational Design
Chapter 11: Leading an Ethical Organization: Corporate Governance, Corporate Ethics, and Social Responsibility
About the Author / Editorial and Production Teams
Version Notes
Glossary This work is published by Virginia Tech’s Pamplin College of Business in association with Virginia Tech Publishing. Suggested citation
Kennedy, Reed. (2020) Strategic Management. Blacksburg, VA: Virginia Tech Publishing. https://doi.org/10.21061/strategicmanagement CC BY NC-SA 3.0 Contributors
About the previous author
The publisher of the 2010 version of this book requested that they and the original author not receive attribution.
This Version
Primary contributor: Reed B. Kennedy
Reviewers / contributors: Eli Jamison, Joseph Simpson, Pankaj Kumar, Ayenda Kemp, Kiran Awate, and Kathleen Manning
Cover design, illustration, and alternative text; student reviewer: Kindred Grey
Research and editorial assistant; student reviewer: Kathleen Manning
Managing editor: Anita Walz
Production editor: Robert Browder
Copyeditors: Grace Baggett, Lauren Holt DOI: https://doi.org/10.21061/strategicmanagement
ISBN 978-1-949373-94-3 (print-color)
ISBN 978-1-949373-89-9 (print-black & white)
ISBN 978-1-949373-96-7 (ebook-PDF)
ISBN 978-1-949373-95-0 (ebook-Pressbooks) https://pressbooks.lib.vt.edu/strategicmanagement Accessibility
Virginia Tech Publishing is committed to making its publications accessible in accordance with the Americans with Disabilities Act of 1990. The HTML and screen reader–friendly PDF versions of this book utilize header structures and include alternative text which allow for machine-readability. - Topological Chaos and Periodic Braiding of Almost-Cyclic SetsStremler, Mark A.; Ross, Shane D.; Grover, Piyush; Kumar, Pankaj (American Physical Society, 2011-03-18)In certain (2 + 1)-dimensional dynamical systems, the braiding of periodic orbits provides a framework for analyzing chaos in the system through application of the Thurston-Nielsen classification theorem. Periodic orbits generated by the dynamics can behave as physical obstructions that "stir" the surrounding domain and serve as the basis for this topological analysis. We provide evidence that, even in the absence of periodic orbits, almost-cyclic regions identified using a transfer operator approach can reveal an underlying structure that enables topological analysis of chaos in the domain.
- Topological chaos, braiding and bifurcation of almost-cyclic setsGrover, Piyush; Ross, Shane D.; Stremler, Mark A.; Kumar, Pankaj (American Institute of Physics, 2012-12-01)In certain two-dimensional time-dependent flows, the braiding of periodic orbits provides a way to analyze chaos in the system through application of the Thurston-Nielsen classification theorem (TNCT). We expand upon earlier work that introduced the application of the TNCT to braiding of almost-cyclic sets, which are individual components of almost-invariant sets [Stremler et al., "Topological chaos and periodic braiding of almost-cyclic sets," Phys. Rev. Lett. 106, 114101 (2011)]. In this context, almost-cyclic sets are periodic regions in the flow with high local residence time that act as stirrers or " ghost rods" around which the surrounding fluid appears to be stretched and folded. In the present work, we discuss the bifurcation of the almost-cyclic sets as a system parameter is varied, which results in a sequence of topologically distinct braids. We show that, for Stokes' flow in a lid-driven cavity, these various braids give good lower bounds on the topological entropy over the respective parameter regimes in which they exist. We make the case that a topological analysis based on spatiotemporal braiding of almost-cyclic sets can be used for analyzing chaos in fluid flows. Hence, we further develop a connection between set-oriented statistical methods and topological methods, which promises to be an important analysis tool in the study of complex systems.