572 research outputs found
sj-docx-1-hol-10.1177_09596836231183110 – Supplemental material for Holocene precipitation hydrogen isotopic values on Nilgiri Plateau (southern India) suggest a combined effect of precipitation amount and transport paths
No full textSupplemental material, sj-docx-1-hol-10.1177_09596836231183110 for Holocene precipitation hydrogen isotopic values on Nilgiri Plateau (southern India) suggest a combined effect of precipitation amount and transport paths by Shreyas Managave, Yongsong Huang, Jean-Pierre Sutra, Krishnamurthy Anupama and Srinivasan Prasad in The Holocene</p
GPU-accelerated depth map generation for X-ray simulations of complex CAD geometries
No full textInteractive x-ray simulations of complex computer-aided design (CAD) models can provide valuable insights for better interpretation of the defect signatures such as porosity from x-ray CT images. Generating the depth map along a particular direction for the given CAD geometry is the most compute-intensive step in x-ray simulations. We have developed a GPU-accelerated method for real-time generation of depth maps of complex CAD geometries. We preprocess complex components designed using commercial CAD systems using a custom CAD module and convert them into a fine user-defined surface tessellation. Our CAD module can be used by different simulators as well as handle complex geometries, including those that arise from complex castings and composite structures. We then make use of a parallel algorithm that runs on a graphics processing unit (GPU) to convert the finely-tessellated CAD model to a voxelized representation. The voxelized representation can enable heterogeneous modeling of the volume enclosed by the CAD model by assigning heterogeneous material properties in specific regions. The depth maps are generated from this voxelized representation with the help of a GPU-accelerated ray-casting algorithm. The GPU-accelerated ray-casting method enables interactive (> 60 frames-per-second) generation of the depth maps of complex CAD geometries. This enables arbitrarily rotation and slicing of the CAD model, leading to better interpretation of the x-ray images by the user. In addition, the depth maps can be used to aid directly in CT reconstruction algorithms.This proceeding may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This proceeding appeared in Grandin, Robert J., Gavin Young, Stephen D. Holland, and Adarsh Krishnamurthy. "GPU-accelerated depth map generation for X-ray simulations of complex CAD geometries." In AIP Conference Proceedings, vol. 1949, no. 1, p. 190002. AIP Publishing LLC, 2018, and may be found at
DOI: 10.1063/1.5031636.
Copyright 2018 Author(s).
Posted with permission
NURBS-Diff: A Differentiable Programming Module for NURBS
No full textBoundary representations (B-reps) using Non-Uniform Rational B-splines (NURBS) are the de facto standard used in CAD, but their utility in deep learning-based approaches is not well researched. We propose a differentiable NURBS module to integrate NURBS representations of CAD models with deep learning methods. We mathematically define the derivatives of the NURBS
curves or surfaces with respect to the input parameters (control points, weights, and the knot vector). These derivatives are used to define an approximate Jacobian used for performing the “backward” evaluation to train the deep learning models. We have implemented our NURBS module using GPU-accelerated algorithms and integrated it with PyTorch, a popular deep learning
framework. We demonstrate the efficacy of our NURBS module in performing CAD operations such as curve or surface fitting and surface offsetting. Further, we show its utility in deep learning for unsupervised point cloud reconstruction and enforce analysis constraints. These examples show that our module performs better for certain deep learning frameworks and can be directly integrated with any deep-learning framework requiring NURBS.This is a manuscript of the article published as Prasad, Anjana Deva, Aditya Balu, Harshil Shah, Soumik Sarkar, Chinmay Hegde, and Adarsh Krishnamurthy. "NURBS-diff: A differentiable programming module for NURBS." Computer-Aided Design 146 (2022): 103199. doi: https://doi.org/10.1016/j.cad.2022.103199
Incorporation of composite defects from ultrasonic NDE into CAD and FE models
No full textFiber-reinforced composites are widely used in aerospace industry due to their combined properties of high strength and low weight. However, owing to their complex structure, it is difficult to assess the impact of manufacturing defects and service damage on their residual life. While, ultrasonic testing (UT) is the preferred NDE method to identify the presence of defects in composites, there are no reasonable ways to model the damage and evaluate the structural integrity of composites. We have developed an automated framework to incorporate flaws and known composite damage automatically into a finite element analysis (FEA) model of composites, ultimately aiding in accessing the residual life of composites and make informed decisions regarding repairs. The framework can be used to generate a layer-by-layer 3D structural CAD model of the composite laminates replicating their manufacturing process. Outlines of structural defects, such as delaminations, are automatically detected from UT of the laminate and are incorporated into the CAD model between the appropriate layers. In addition, the framework allows for direct structural analysis of the resulting 3D CAD models with defects by automatically applying the appropriate boundary conditions. In this paper, we show a working proof-of-concept for the composite model builder with capabilities of incorporating delaminations between laminate layers and automatically preparing the CAD model for structural analysis using a FEA software.This proceeding may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This proceeding appeared in Bingol, Onur Rauf, Bryan Schiefelbein, Robert J. Grandin, Stephen D. Holland, and Adarsh Krishnamurthy. "Incorporation of composite defects from ultrasonic NDE into CAD and FE models." AIP Conference Proceedings 1806, no. 1, (2017): 150004. , and may be found at DOI: 10.1063/1.4974728. Posted with permission.</p
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Online Fundraising Through the Lenses of Law, Economics, and Sociology: Examples from American P2P Lending and Thai Rotating Savings and Credit Association
No full textIn recent years, online lending has become a new method of financing that allows people to lend and borrow anywhere anytime. Yet, due to its complex and wide-ranging operation, the online lending phenomena has become one of the most buzzing regulatory concerns. Online lending not only challenges incumbent loan providers like commercial banks by providing loans to unserved borrowers at attractive rates, it also presents unprecedented investment opportunities for individual lenders who are often referred to as ‘peer’ or ‘crowd’ to lend out their money commercially. In this dissertation, I explore how two different online lending methods help individual lenders who often lack financial sophistication to make safe investment and how laws and regulations may affect online lending businesses and their consumers. This dissertation includes two essays that examine two examples of online lending practices: peer-to-peer (P2P) lending in the United States and online rotating savings and credit association (ROSCA) in Thailand. The first essay argues P2P lending platforms originally endorsed interpersonal relationships in lending and adopted many peer-to-peer features, such as social networks, personal profiles and group affiliations because interpersonal relationships are valuable and imperative for individual lenders and borrowers on P2P lending platforms. Nevertheless, the laws and regulations on P2P lending in the United States have caused P2P lending platforms to relinquish their commitments to utilize interpersonal relationships. The disappearance of interpersonal relationship on P2P lending platforms results in worse economic and sociological outcomes for individual lenders.The second essay argues that interpersonal relationship is paramount to the success of ROSCAs in Thailand. Traditionally, ROSCA participants rely on their interpersonal relationships to lend and borrow from each other. Recently, an online form of ROSCAs has emerged and spread. Online ROSCAs allow strangers, who have no interpersonal relationship to easily create a virtual ROSCA. Such a risk alarms the financial regulators, lawmakers, and the public. Nevertheless, the current regulatory landscape on ROSCAs have also been developed based on a long concern of frauds created by informal fundraising methods. While the current regulatory regime aims to ban and restrict ROSCAs which are operate beyond a local and personal level, the regulations effectively deem the whole category of online ROSCAs illegal and drove them to operate outside to the formal financial system. Both P2P lending in the United States and ROSCAs in Thailand utilize interpersonal relationships among parties of lending transaction to address four fundamental concerns in lending: uncertainty, information asymmetry, interpersonal trust, and institutional trust. From an economic perspective, Ronald Coase’s proposition suggests that personal relationships may help reduce uncertainty and information asymmetry in economic transactions including lending. From a sociological perspective, Francis Fukuyama and Linda Molm acknowledge the importance of interpersonal trust and institutional trust within financial exchanges. Interpersonal relationships among actors of a financial transaction can build and maintain interpersonal trust and institutional trust. This dissertation also applies both the economic and sociological perspectives to understand how laws and regulations might affect P2P lending platforms, and traditional and online ROSCAs. The studies of P2P lending platforms and online ROSCAs exemplify how the current laws and regulations which were developed based on more traditional financial methods can shift new financial services, particularly online lending, into a worse position
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A Risk/Benefit Analysis of Central Clearing of Over-the-Counter (OTC) Derivatives and a Chaos Theory-Based Perspective on Clearing Mandates
No full textIn the aftermaths of the global financial crisis of 2007-2009 (GFC), policymakers and regulators around the world embarked on far-reaching reforms of the over-the-counter (OTC) derivatives market. A key element in their agenda was the introduction of central clearing mandates for OTC derivatives, which was largely driven by the belief shared among policymakers and regulators that central counterparties clearing OTC derivatives (OTC CCPs) could reduce the counterparty risk and mitigate the systemic risk associated with their trading. During the past seven years, however, the scale and complexity of the process of implementation of central clearing mandates of OTC derivatives have gradually emerged. In particular, a dawning debate has arisen around the question of how OTC CCPs may themselves generate and/or exacerbate systemic risk within the financial system. The present work investigates this question in detail. After providing some background on OTC derivatives and related financial risks, the present work examines the operations and functions of OTC CCPs, covering aspects such as novation, margins, multilateral netting and the coordinated default management process. Following this preliminary analysis, the present work discusses multiple benefits and risks of OTC CCPs and, then, investigates relationships and dynamic interactions existing among them. This risk/benefit analysis of OTC CCPs, in turn, helps gain a realistic appreciation of OTC CCPs’ systemic-risk implications. Significantly, a number of procedures and mechanisms through which OTC CCPs can generate and/or exacerbate systemic risk are identified, which include the following:• OTC derivatives trading through OTC CCPs may create excessive concentration of multiple risks into one single focal point. This reduces the possibility for diversification and may increase the probability that the failure of an OTC CCP could have system-wide destabilizing effects. Furthermore, by concentrating the risk associated with the trades being cleared, OTC CCPs may themselves become systemically important entities and their failure may expose many market participants to severe losses. • By changing the topology of the network of connections in the OTC derivatives market, OTC CCPs essentially replace one set of interconnections with another, which could be as vulnerable to systemic failures as (or even more vulnerable than) the one existing prior to the implementation of central clearing mandates. The resulting interconnected structure is, then, made even more complex by the raise of “alternative forms” of clearing of OTC derivatives, which have emerged over the past few years driven by unprecedented developments in new technologies, including blockchain and hyperledger technologies.• Rigorous margin requirements enforced by OTC CCPs may have the effect of increasing operational complexity and rigidity within the OTC derivatives market, which, in turn, may lead to a more tightly coupled financial system. In addition, as shown in the aftermaths of the Brexit vote, OTC CCPs’ rigorous margining may create pro-cyclicality problems, and in the event of large price moves it may trigger “systemic margin calls.” In such a scenario, many OTC CCPs’ members (CMs) with losing positions would be required to make large variation margin payments in a very tight frame, and would be forced to raise funds simultaneously. This rush to liquidity may, then, create severe strains for CMs with destabilizing effect for OTC CCPs, as well. Moreover, the need to raise liquidity to meet large margin calls and the need to reduce (or close) positions because of the inability to meet such calls may create tight coupling and may lead to chaotic fire sales that further exacerbate price movements. The fire sales of assets may have spillover adverse effects that go far beyond derivatives transactions to impact any institution or firm holding the assets subject to fire sales, including those that don’t have any (direct or indirect) counterparty exposure to market participants trading cleared derivatives. Last, uncertainty about the solvency of market participants may induce chaotic information contagion and further assets liquidations, which may exacerbate price volatility and may result into severe declines in trading market liquidity.• Multilateral netting and setoff through OTC CCPs change creditor priority by increasing the priority of the OTC CCP and the derivatives counterparties over other claimants on a defaulted CM. In so doing, multilateral netting and setoff through OTC CCPs essentially redistribute value from one group of creditors to other creditors and re-allocate risks of losses from one set of claimants to another. This redistributive effect may be systemically damaging if the risk is transferred to parties that are as systemically important and as vulnerable as (or even more systemically important and more vulnerable than) OTC derivatives market participants. • OTC CCPs’ loss mutualization and risk sharing mechanisms may expose OTC CCPs to problems of adverse selection and moral hazard, and may increase the opacity of OTC derivatives trading, which, in turn, may create the risk of runs on OTC CCPs in the event of default of one or more of their CMs. In addition, margining and risk-sharing mechanisms of OTC CCPs make them particularly vulnerable to wrong-way risk (WWR), thus contributing further instability.• A typical OTC CCP’s default waterfall resembles the loss allocation structure of a collateralized debt obligation (CDO) as the various levels in an OTC CCP’s default waterfall are typically accessed in sequence, much like the tranches of a CDO. As a result, the risk characteristics of the two structures may be very similar. In particular, much like senior and super-senior tranches in a CDO, the risk exposure of CMs via an OTC CCP’s default fund is heavily concentrated in terms of systemic risk and WWR and it may increase significantly during periods of large market-wide shocks, high volatility and liquidity shortage. By building on the findings of the described risk/benefit analysis of OTC CCPs, the present works examines a new approach to systemic risk-related financial regulation, which has emerged in the aftermaths of the GFC and has been inspired by chaos theory, and applies this new approach onto the OTC derivatives clearing context through a two-step analysis. First, the present work focuses on the OTC CCP’s coordinated default management process and discusses how to improve it by considering behavior aspects in the pricing and structuring of an OTC CCP’s default waterfall. In particular, the present work examines innovative designs of OTC CCPs’ pre-funded mutualized default fund(s), which can create the necessary incentives for CMs to cooperate and help the OTC CCP during the coordinated default management process by participating actively in the hedging and auctioning of the defaulted CM's positions. Second, the present work identifies and discusses additional resources and stabilizing mechanisms that could be activated in the remote (but still possible) scenario in which an OTC CCP’s coordinated default management process backfires, including contingent capital, central bank’s liquidity resources, private systemic risk insurance fund(s), third-party systemic risk insurance, and systemic risk catastrophe bonds
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Establishing the Legal Framework for Crowdfunding in China
No full textCrowdfunding is a rapidly growing means of raising capital from a largecrowd of people via the internet. In the U.S., Title III of the JOBS Act exempts
offerings using crowdfunding from registering with SEC. To implement the
statutory exemption, SEC issued Regulation Crowdfunding (Reg CF). Reg CF
imposes certain obligations on issuers, investors, and funding portals.
Now in the U.S., offerings using crowdfunding proliferate. Among all
these offerings, common stock, debt, and Simple Agreement for Future Equity
(SAFE) are the most-issued types of securities. Revenue sharing note becomes
a marked type of debt securities. The SAFE is a convertible security that can
convert into equity security, in most cases, preferred stock. It is widely used in
crowdfunding offerings and has two variants. Meanwhile, it also gives rise to
suspicion over its safety, and even SEC’s failed attempt to ban its use in
crowdfunding offerings. However, its popularity shows no sign of decline.
In contrast, in China, crowdfunding industry used to prosper but now is
dying due to regulatory clampdown. To resurrect the industry, two legal
loopholes in China Securities Law (CSL) should be corrected. The first is only
a modicum of securities are governed by CSL. Notes and SAFEs are outside of
CSL’s reach. The second is CSL’s numeric benchmark for a public offering is
neither scientific nor reasonable. But overall, the priority is to provide a
statutory exemption for crowdfunding offerings in China. Reg CF and a rich
body of relevant cases in the U.S. could be useful for China’s rulemaking
undertakings in crowdfunding
An Intelligent Approach of Knowledge Searching within Internet-Based Distributive Knowledge Integrated Environment
No full textDifferentiable Spline Approximations
No full textThe paradigm of differentiable programming has significantly enhanced the scope of machine learning via the judicious use of gradient-based optimization. However, standard differentiable programming methods (such as autodiff) typically require that the machine learning models be differentiable, limiting their applicability. Our goal in this paper is to use a new, principled approach to extend gradient-based optimization to functions well modeled by splines, which encompass a large family of piecewise polynomial models. We derive the form of the (weak) Jacobian of such functions and show that it exhibits a block-sparse structure that can be computed implicitly and efficiently. Overall, we show that leveraging this redesigned Jacobian in the form of a differentiable "layer" in predictive models leads to improved performance in diverse applications such as image segmentation, 3D point cloud reconstruction, and finite element analysis.This is a proceeding preprint from Cho, Minsu, Aditya Balu, Ameya Joshi, Anjana Deva Prasad, Biswajit Khara, Soumik Sarkar, Baskar Ganapathysubramanian, Adarsh Krishnamurthy, and Chinmay Hegde. "DIFFERENTIABLE SPLINE APPROXIMATIONS." arXiv preprint arXiv:2110.01532 (2021). doi: https://doi.org/10.48550/arXiv.2110.01532. Copyright 2021 The Authors
Optogenetic control of developmental signaling pathways
No full textHow a complex multicellular organism forms from a single cell is a question that defies simplistic understanding. Yet, embryonic developmental programs use a surprisingly small set of signaling pathways to pattern the embryonic tissue into germ layers from which the various tissues and organs emerge. A hallmark of embryonic development is that these recurring developmental signaling pathways are carefully orchestrated in space and time to facilitate proper development. Understanding the spatiotemporal intricacies of these pathways necessitates tools which enable their perturbation in precisely defined spatiotemporal patterns. Optogenetics uses light-induced conformational changes to enable or disable protein-protein interactions, thereby permitting control of signal transduction at the flip of a switch. Consequently, light is emerging as a powerful tool to study embryonic development owing to its rapid, reversible and residue-free application, which empowers the researcher with excellent spatial and temporal control of signaling. Here, I first review recent accomplishments in optical microscopy and optogenetics which highlight the dual roles of light in visualizing as well as perturbing cellular microenvironments and processes. Second, I present an optogenetic approach to control the mitogen-activated protein kinase (MAPK) pathway which we successfully applied in both neuroblasts and frog embryos. Third, I demonstrate an optogenetic approach to control the Wnt signaling pathway in mammalian cells and frog embryos. Finally, I propose and provide working proof for a generalizable optogenetic platform to control those developmental signaling pathways, the activities of which involve the homo-association of plasma membrane-localized receptor tyrosine kinases.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2021-12-01The student, Vishnu Vardhan Krishnamurthy, accepted the attached license on 2019-11-27 at 10:27.The student, Vishnu Vardhan Krishnamurthy, submitted this Dissertation for approval on 2019-11-27 at 10:29.This Dissertation was approved for publication on 2019-12-04 at 10:19.DSpace SAF Submission Ingestion Package generated from Vireo submission #14554 on 2020-02-28 at 17:36:14Made available in DSpace on 2020-03-02T22:38:43Z (GMT). No. of bitstreams: 3
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