18 research outputs found
Online Machine Learning for Graph Topology Identification from Multiple Time Series
No full textHigh dimensional time series data are observed in many complex systems. In networked data, some of the time series are influenced by other time series. Identifying these relations encoded in a graph structure or topology among the time series is of paramount interest in certain applications since the identified structure can provide insights about the underlying system and can assist in inference tasks. In practice, the underlying topology is usually sparse, that is, not all the participating time series in influence each other. The goal of this dissertation pertains to study the problem of sparse topology identification under various settings.
Topology identification from time series is a challenging task. The first major challenge in topology identification is that the assumption of static topology does not hold always in practice since most of the practical systems are evolving with time. For instance, in econometrics, social networks, etc., the relations among the time series can change over time. Identifying the topologies of such dynamic networks is a major challenge.
The second major challenge is that in most practical scenarios, the data is not available at once - it is coming in a streaming fashion. Hence, batch approaches are either not applicable or they become computationally expensive since a batch algorithm is needed to be run when a new datum becomes available.
The third challenge is that the multi-dimensional time series data can contain missing values due faulty sensors, privacy and security reasons, or due to saving energy.
We address the aforementioned challenges in this dissertation by proposing online/-batch algorithms to solve the problem of time-varying topology identification. A model based on vector autoregressive (VAR) process is adopted initially. The parameters of the VAR model reveal the topology of the underlying network. First, two online algorithms are proposed for the case of streaming data. Next, using the same VAR model, two online algorithms under the framework of online optimization are presented to track the time-varying topologies. To evaluate the performance of propose online algorithms, we show that both the proposed algorithms incur a sublinear static regret. To characterize the performance theoretically in time-varying scenarios, a bound on the dynamic regret for one of the proposed algorithms (TIRSO) is derived. Next, using a structural equation model (SEM) for topology identification, an online algorithm for tracking time-varying topologies is proposed, and a bound on the dynamic regret is also derived for the proposed algorithm. Moreover, using a non-stationary VAR model, an algorithm for dynamic topology identification and breakpoint detection is also proposed, where the notion of local structural breakpoint is introduced to accommodate the concept of breakpoint where instead of the whole topology, only a few edges vary. Finally, the problem of tracking VAR-based time-varying topologies with missing data is investigated. Online algorithms are proposed where the joint signal and topology estimation is carried out. Dynamic regret analysis is also presented for the proposed algorithm. For all the previously mentioned works, simulation tests about the proposed algorithms are also presented and discussed in this dissertation. The numerical results of the proposed algorithms corroborate with the theoretical analysis presented in this dissertation
New consistency orchestrators for emerging distributed systems
No full textWe are gradually becoming more dependent on various distributed systems, e.g., smart home management systems, bank management, traffic monitoring, etc. Some run on data-centers while others run on edge devices, e.g., smart home applications. In all these environments, efficiently maintaining consistency across such a large number of components is a hard challenge.
Consistency ensures a coherent view across the disparate components of a distributed system. An inconsistent view might lead to various issues that directly impact user experience. For example, in a database management system, an inconsistent view of a primary replica might make the system slow, or show stale data to users. If a bank account has two primary-replicas, each of them might show their own version of the account balance -- this leads to incorrect banking transactions. Similarly, in a smart home, failing to isolate concurrent routines (sequence of commands) might end the home in a state not consistent with the user's expectation. E.g., the outcome of two concurrent routines R1 = {Turn all light ON} and R2 = {Turn all light OFF} might end up in a state where some of the lights are ON while others are OFF.
Addressing this requires the disparate components of a distributed system to have coordination. Such coordination includes maintaining a consistent view of the failed nodes, leader election, consistent primary replica selection, coherence in smart home's current state, etc. Orchestrators are dedicated entities that use specialized protocols (e.g., Chubby, ZooKeeper etc.) to help coordinate the components.
Distributed systems can use i) generic external orchestrators such as Zookeeper, Chubby etc., or 2) build their own internal orchestrator. Unlike external orchestrators, internal orchestrators avoid external dependencies and are flexible and modifiable, e.g., making it relatively easier to provide complex consistency guarantees and providing consistent and reliable distributed data-structures.
In this thesis we present new internal orchestrators for maintaining consistency in both edge-based and cloud-based distributed systems. This thesis has the following contributions: for edge-based distributed systems, we develop a smart home orchestrator called SafeHome that offers a congruent end state by guaranteeing stronger properties, e.g., Isolation, Atomicity, Safety. This is an improvement over the best-effort philosophy used in today's smart homes which leads to incongruent states. Second, For cloud-based distributed systems, we reveal and analyze Service Fabric's consistent and scalable failure detector, which is the heart of its internal orchestration mechanisms. Third, we present a new way to decentralize SF's arbitration technique and design a consistent failure detector on top of it, which offers identical consistency guaranties as SF's centralized scheme. We also provide formal proof of correctness and time-bound for both central and distributed arbitrator schemes.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2022-05-01The student, Shegufta Ahsan, accepted the attached license on 2020-05-01 at 15:22.The student, Shegufta Ahsan, submitted this Dissertation for approval on 2020-05-01 at 15:39.This Dissertation was approved for publication on 2020-05-03 at 18:48.DSpace SAF Submission Ingestion Package generated from Vireo submission #15157 on 2020-08-25 at 17:28:36Made available in DSpace on 2020-08-26T23:57:22Z (GMT). No. of bitstreams: 3
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Trust-building mechanisms in Abu Hamed al-Gharnati's travelogues based on "The Delicate of Hearts"
No full textAbu Hamed al-Gharnati has written two travelogues in the field of Arabic travel writing, entitled "The Delicate of Hearts and Elite Admiration" and "Expressed some of the Morocco’s wonders". A unique feature of both travelogues is their wonder-taking, meaning that the travel writer seeks to narrate amazing events and to focus on scenes that surprise us. For this reason, he uses the word "wonders" in the title of his travelogue. This approach of the author delays the reader and makes them consider them superstitious stories that have no real context. Ghranati, who is fascinated by the remarkable observations, realizes this and uses various mechanisms to reassure the reader and create a real world for him while dealing with strange stories. The present study intends to use the descriptive-analytical method to examine the mechanisms of building trust, their tools and goals in the travelogue of "The Delicate of Hearts". Findings indicate that these methods of building trust, along with related tools, are reflected in various ways in this travelogue, such as: A: Transmission of visual and audio content. B: Taking care in inserting their sources and narrations. C: Creating a logical atmosphere in the process of narration and anecdote. It is worth noting that in this book, there are also news and anecdotes that the author has not presented with a reliable structure and ,therefore, lack trust-building tools. The reason for this seems to be that the author seeks to gradually gain the reader's confidence in his method of citation by providing reassuring patterns. Of course, this phenomenon is faint and the distinctive style in the Gharnati’s narrative method is the use of trust building approach
Seroprevalence of toxoplasmosis and current thinking regarding screening in pregnancy: A review of the literature and case study discussion
No full textThe approach to the diagnosis and treatment of congenital toxoplasmosis has been one of flux and debate, fueled by lack of knowledge, lack of consensus, different methods of screening and different national policies for screening in different parts of the world. Countries with higher prevalence of disease such as in Europe and South America have a heightened awareness of the need to screen and treat for this parasitic infection during pregnancy. In contrast, in the United States, it is a condition scarcely discussed and has been largely ignored except in some large centers and by a few researchers. Policies and research strategies for any condition should start with obtaining good data. The aims of this thesis included a review of prevalence studies conducted in the United States, focused on the past 20 years, combined with a description of original research conducted by the author several years ago. The latter was a cross-sectional study performed in Houston, one of the largest American cities with a great ethnic mix. The study analyzed prevalence rates of Toxoplasma gondii IgG antibody in sera of women of reproductive age. Overall seroprevalence was 12.3%. In keeping with other studies, higher prevalence correlated with lower socioeconomic status, Black and Hispanic and Asian ethnicities, and increasing age. A literature search revealed only three prevalence studies performed in the United States over the past 20 years, with another four studies only referred to as personal communications or within a textbook, without further study detail available. The literature review also revealed a lack of consensus on whether or not to screen for toxoplasmosis in pregnancy, and even whether or not treatment in utero is worthwhile. Proponents of screening and treatment in pregnancy site studies both in the United States and France, emphasize that treatment reduces disease manifestations in infants. Opponents cite other studies that show only marginal benefits, together with potential side effects of medication regimens and generation of anxiety in parents. What is agreed on so far is the value of educating pregnant women on how to avoid contracting toxoplasmosis, and educating physicians on making the best use of reference laboratories before major treatment decisions are made. Further research to reevaluate the literature critically, review new treatment regimens and examine costs and benefits of screening and treatment of toxoplasmosis in pregnancy, bringing together European and American researchers, is needed
The phytochemical investigation and biological activity of Nepeta clarkei
No full textThe present study is aimed at the isolation and identification of the compounds responsible for the bioactive behavior of Nepeta clarkei (Hook. f). The crude extract and its various sub-fractions obtained from N. clarkei Hook. f. (chloroform (NCC), n-hexane (NCH), ethyl acetate (NCE), and aqueous (NCW)) along with methanolic extract were screened for anti-cancer activity. Only NCH and NCC fractions suppressed the cancer cell lines (HT29 and HCT116) to less than 20% and were screened for a range of other biological activities (antiglycation, phytotoxicity, antiplattelt, insecticidal and antimicrobial) in vitro. The chloroform fraction exhibited significant (63.31%) antiglycation activity followed by the n-hexane fraction (43.9%). Interestingly n-hexane fraction demonstrated a significant phytotoxic potential (100% inhibition) towards Lemna minor at the highest concentration (1000 µg/mL) only, while the chloroform fraction showed moderate activity (33.83%). The n-hexane fraction furthermore demonstrated 100% anti-platelet activity against AA (48 µg/mL) and PAF (15 µg/mL). On the other hand both the chloroform and n-hexane fractions were inactive against fungi and bacteria used in the anti-bacterial and anti-fungal assays. The order of toxicity towards brine shrimps was n-hexane > chloroform fractions. An intensive phytochemical investigation of the chloroform extract of N. clarkei resulted in the isolation of nine metabolites including 1,2-benzenedicarboxylic acid bis (2-ethylhexyl) diester (1), eupatorin (2), achillin (3), neoponcirin (4), parvifloroside B (5), decipinol ester A (6), betulinic acid (7), b-sitosterol (8), and β-sitosterol glucopyranoside (9). The structure elucidation was carried out on the basis of 1D (1H- and 13C) and 2D (H-C correlations; HMBC, HSQC) NMR techniques and confirmed by comparison of their physical and spectroscopic data with those reported in literature. All these compounds, to the best of our knowledge, were isolated from N. clarkei for the first time
A CASE FOR ADDING AN INSPECTION LEVEL RELATED TO SHM FOR BRIDGE EVALUATION
No full textThe Canadian Highway Bridge Design Code (CHBDC) uses the concept of a target reliability index for evaluating the load carrying capacity of existing bridges. This index, which is based on risk to human life, relates to three aspects of uncertainties inherent in a bridge; (a) element behaviour, (b) system behavior, and (c) inspection level, where the inspection level currently refers to only manual inspections. Citing examples of tests on many instrumented bridges, the paper proposes an additional inspection level for inspections done with the help of electronic instruments and tests under controlled vehicle loads. The paper proposes simple additions to clauses of the CHBDC, for use when determining the optimum load carrying capacities of existing bridges where structural health monitoring (SHM) information is available.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
Experimental and field investigation of a bridge-weigh-in-motion (BWIM) system. Improving the accuracy of bridge inspection, evaluation, and fatigue assessment
No full textBridges are vital component of a country’s transportation system and its economy. However, large number of ageing bridges are either structurally or geometrically deficient in some way. In recent years, the remaining life of ageing bridges, were calculated by detailed evaluation and damage assessment using structural health monitoring (SHM) techniques integrating bridge-weigh-in-motion (BWIM) systems. The field study of an existing BWIM system in Winnipeg, Manitoba was conducted on the Prototype Bridge. This work was extended to analysis and comparison of the algorithms adopted on the Prototype Bridge which provided deep insight in identifying the sources of error in BWIM systems. It was followed by a study on fatigue assessment of steel girder bridges. This research contributes by incorporating field measurements from BWIM system on the Prototype Bridge to estimate fatigue loading and damage assessment.
In analytical phase, a simply supported beam subjected to moving and pulsating load was investigated for signal simulation and filtering in MATLAB. This was done as an initial exercise to understand dynamic effects of the load and its relevance to bridge natural frequency. This work was presented in a conference proceeding, attached in appendix.
The experimental part of this work aims to identify sources of error in BWIM systems with the aid of the Model Bridge and verify area method, tested on the Prototype Bridge. The method was further investigated on the Model Bridge to obtain 95% confidence interval over real bridge BWIM testing. Model bridge structure was fabricated using polycarbonate. The model was designed to have natural frequencies like the Prototype Bridge. It was instrumented at two different locations with piezoelectric sensors for estimating velocity, transverse position, and class of model truck. It was instrumented with electrical strain gauges at three transverse locations for estimating Gross Vehicle Weight (GVW) of model truck. Video camera was used for verifying velocity profile.
Author endeavored to establish relevance of long-term monitoring data obtained from BWIM to bridge evaluation. In this work it was proposed that SHM will add another level of inspection to CHBDC clauses and will improve the estimation of load carrying capacities of existing bridges.May 202
Akbar II as Pretender: A Study in Anarchy
No full textAkbar Shāh, son of the Mughal emperor Shāh 'Ālam II, was elevated to the throne of Delhi as pretender eighteen years previous to his accession as Akbar II, and money was struck in his name. The addition of another claimant to the dynastic list was communicated in a joint paper by Mr. S. H. Hodivala and myself, which appeared in the Journal of the Asiatic Society of Bengal for the year 1922, and to which I invite reference. I had found a copper coin of Aḥmadābād mint bearing the name of Akbar Shāh and date A.H. 1203, which made me conjecture whether Ghulām Qādir Khān, the “unspeakable Rohilla”, raised another prince to the Mughal throne after the puppet Bedār Bakht (A.H. 1202–3), who might or might not be identical with the Akbar Shāh, eldest surviving son of Shāh 'Ālam II, who succeeded his father in the regular way as Akbar II in the year A.H.. 1221 (A.D. 1806). I put the matter to Mr. Hodivala, a leading authority on Mughal history, and his reply was that “it has not yet been possible to find an absolutely complete and satisfactory solution of the problem connected with the Akbar Shāh coins of A.H. 1203, but there would seem to be fairly good grounds for answering the question in the affirmative”. The fullest account of the transactions which led to the deposition and blinding of Shāh 'Ālam II is in the 'Ibratnāmah (Book of Warning) of Faqīr Khairu-d-dīn Muḥammad, but this work closes soon after recounting the terrible cruelties practised on the Emperor Shāh 'Ālam and his family by the infamous Ghulām Qādir, whose atrocities the author describes at length.</jats:p
The Phenyltetraene Lysophospholipid Analog PTE-ET-18-OMe as a Fluorescent Anisotropy Probe of Liquid Ordered Membrane Domains (Lipid Rafts) and Ceramide-Rich Membrane Domains
No full textAuthor manuscript. Published in final edited form as: Biochim Biophys Acta. 2007 September; 1768(9): 2213–2221.The conjugated phenyltetraene PTE-ET-18-OMe (all-(E)-1-O-(15’-Phenylpentadeca-8’,10’,12’,14’-tetraenyl)-2-O-methyl-rac-glycero-3-phosphocholine), is a recently developed fluorescent lysophospholipid analog of edelfosine, (Quesada et al. (2004) J. Med. Chem. 47, 5333–5335). We investigated the use of this analog as a probe of membrane structure. PTE-ET-18-OMe was found to have several properties that are favorable for fluorescence anisotropy (polarization) experiments in membranes, including low fluorescence in water and moderately strong association with lipid bilayers. PTE-ET-18-OMe has absorbance and fluorescence properties similar to those of diphenylhexatriene (DPH) probes, with about as large a difference between its fluorescence anisotropy in liquid disordered (Ld) and ordered states (gel and Lo) as observed for DPH. Also like DPH, PTE-ET-18-OMe has a moderate affinity for both gel state ordered domains and Lo state ordered domains (rafts). However, unlike fluorescent sterols or DPH (Megha and London (2004) J. Biol. Chem. 279, 9997–10004), PTE-ET-18-OMe is not displaced from ordered domains by ceramide. Also unlike DPH, PTE-ET-18-OMe shows only slow exchange between the inner and outer leaflets of membrane bilayers, and can thus be used to examine anisotropy of an individual leaflet of a lipid bilayer. Since PTE-ET-18-OMe is a zwitterionic molecule, it should not be as influenced by electrostatic interactions as are other probes that do not cross the lipid bilayer but have a net charge. We conclude that PTE-ET-18-OMe has some unique properties that should make it a useful fluorescence probe of membrane structure.This work was supported by NIH grant GM 48596 to EL and a Spanish MEC grant BQU2003/04413 to AUA.Peer reviewe
