47 research outputs found
Understanding and assessment of a two-component G-prior in variable selection
Get PDFThe selection of variables in regression problems has occupied the minds of many statisticians. Several Bayesian variable selection methods have been developed, and we concentrate on the following method.This thesis which is a continuation of a project by Zhang textit{et al.} cite{Zha} published in Bayesian Analysis in 2016, first describes the general idea behind Bayes Inference, various sampling methods based on Bayes theorem.Then we present a Bayesian variable selection method based on an extension of the Zellner’s g-prior in linear models. More specifically, we propose a two-component G-prior, wherein a tuning parameter, calibrated by use of pseudo variables, is introduced to adjust the distance between the two components. We Assess the impact of tuning parameter b, the distance between important and unimportant variables, on the selection of variables by controlling Bayesian false model selection rate with respect to unimportant variables based on creating pseudo variables. We show that implementing the proposed prior in variable selection is more efficient than using the Zellner’s g-prior
DESIGN A SYSTEM OF SECURE RANDOM NUMBER GENERATORS BY RANDOM COUPLING WITH THE FUTURE
Get PDFPseudo-random number generators (PRNGs) play an important role in both areas of computersimulation and computer security. For PRNGs in computer security applications, the securityconcern is extremely important. In recent years, there have been many PRNGs proposed in the areaof computer simulation satisfying the nice properties. However, most of them are linear generators,thus sharing the same weakness in predictability. The major aim of this study is to propose threegeneral class of secure generators, called RCF(Random Coupling with Future), Dual RCF, RCFShufflinggenerators, to obtain a secure generator that would inherit the nice properties.Proposed generators are suitable for both simulation and security applications. The keyfeature is to break the linearity structure of some classical linear generators based on coupling the”current” value with a ”future” value that is ”random” steps away. We provide some justificationsand discuss the security, efficiency, and distributional properties of RCF generators. Steps andguidelines on choosing appropriate parameters for creating RCF generators are provided. Severalexamples of well chosen parameters are presented. Finally, some potential extensions for furtherenhancement are briefly discussed
Age at onset of different pubertal signs in boys and girls and differential DNA methylation at age 10 and 18 years: an epigenome-wide follow-up study
No full textSTUDY QUESTION: Is the age of onset of pubertal markers related to subsequent changes in DNA methylation (DNAm)?SUMMARY ANSWER: We identified 273 cytosine-phosphate-guanine (CpG) dinucleotides in girls and 67 CpGs in boys that were related to puberty and that were replicable in two other investigations.WHAT IS KNOWN ALREADY: Previously, 457 CpGs (not gender-specific) and 347 (in girls) and 50 (in boys), respectively, were found to be associated with puberty, according to investigations of studies from Denmark (20 girls and 31 boys) and North America (30 girls and 25 boys).STUDY DESIGN SIZE DURATION: The study was based on a birth cohort of 1456 participants born in 1989/90, with follow-up at age 10 and 18 years.PARTICIPANTS/MATERIALS SETTING METHODS: The follow-up included 470 participants with information on DNAm and age of pubertal onset (244 girls and 226 boys). Age of pubertal onset was ascertained retrospectively at age 18 years. Using the Pubertal Development Scale, both genders were asked about ages of onset of growth spurt, body hair growth and skin changes. Ages at voice deepening and growth of facial hair were inquired from boys; ages at breast development and menarche from girls. Blood samples were collected at 10 and 18 years of age. DNA was extracted using a standard salting out procedure. The methylation level for each CpG site was assessed using one of two different platforms. DNAm was measured by a ratio of intensities denoted as
β values for each CpG site. After quality control, 349 455 CpG sites were available for analysis.
M values were calculated (log2(
β/(1-
β)) to approximate a normal distribution, and their levels were adjusted for blood cell proportions. Linear mixed models were applied to test the association between age of pubertal markers and repeated measurement of DNAm at 10 and 18 years.
MAIN RESULTS AND THE ROLE OF CHANCE: In girls, a total of 63 019 CpGs statistically significantly changed after occurrence of any of the five pubertal events and 13 487 were changed subsequent to all five events: the respective number is boys were 3072 and 301. To further exclude false-positive findings, we investigated which CpGs were replicable in prior studies from Denmark or North America, resulting in 273 replicable CpG in girls and 67 CpGs in boys (236 and 68 genes, respectively). Most identified genes are known to be related to biological processes of puberty; however, genetic polymorphisms of only four of these genes were previously linked to pubertal markers in humans.LIMITATIONS REASONS FOR CAUTION: The relative age of pubertal onset to the age of DNAm measurements does not allow causal inference, since DNAm at an earlier age may have affected the pubertal age or pubertal age may have altered later DNAm. This investigation concentrates on autosomes. CpGs on X and Y chromosomes are not included in the current study.WIDER IMPLICATIONS OF THE FINDINGS: Assessment of biological processes involved in pubertal transitions should include epigenetic information. Differential DNAm related to puberty needs to be investigated to determine whether it can act as an early marker for adult diseases known to be associated with puberty.STUDY FUNDING/COMPETING INTERESTS: This work was supported by NIH grants R03HD092776 (Epigenetic characterization of pubertal transitions) and R01AI121226. The 10-year follow-up of this study was funded by National Asthma Campaign, UK (Grant No 364), and the 18-year follow-up by a grant from the National Heart and Blood Institute (R01 HL082925). The authors have no conflicts to report.</p
Towards uncertainty in micro-grids: planning, control and investment
No full textThe advent of micro-grids and their potential participation in the wholesale market makes the development of new business models necessary. It is anticipated that the future wholesale market for electricity and its ancillary services will include the existing major players as well as microgrids, which will act both as buyers and sellers. The wholesale market will shift more towards a distributed system with the centers of gravity dynamically changing depending on how the smaller micro-grids play out their supply and demand and also how the market aggregation takes place. Having the obligation to fully satisfy its demand at each point of time, any shortage in available power supply within the micro-grid will lead to the purchase of electricity from the macro-grid at spot market price. The sources of variability rising from the forecast of renewable energy resources and electricity demand, would introduce uncertainty in making decisions at planning layer. Also, a micro-grid may fail to honor its contractual obligations to supply to the market due to these volatilities.To optimize the planning and operation of micro-grids, it is important for the planner and controller to take into account uncertainties inherent to the microgrid and the overall supply and demand network, including the energy market place. With high capital costs involved in building a micro-grid, sequential investment strategies, which promote gradual increase in capacity of generation, are needed. This work aims to develop a set of models and tools that address the optimal decision-making processes involved in both operation and investment in micro-grids. These models account for short-term operational and long-term investment uncertainties in decision making and adopt the following analytics: Two-stage stochastic programming and certainty equivalent models to obtain optimal decisions for day-ahead planning in micro-grid’s operation; Contingent claim analysis and Monte Carlo simulation to examine the value in delaying the investment due to uncertainty around the investment; Capital budget planning model along with Monte Carlo stochastic scenario generation to derive the optimal investment decisions for micro-grid’s portfolio considering its optimal operation under uncertainty.M.S.Includes bibliographical referencesby Farnaz Farza
Interaction of microwave filaments and blunt body in supersonic flow
No full textRecent experiments have demonstrated the capability of pulsed microwave energy deposition for drag reduction in supersonic flows. The principal mechanism of this phenomenon is the interaction of the hot filaments generated by the microwave energy pulse with the shock system formed by the aerodynamic body. In this work, the filament is modeled as a thin fluid region of high temperature. The interaction of the filament(s) with a cylindrical body at Mach number 1.89 is examined using the unsteady Euler equations. Two filament structures are considered, namely, 1) an infinitely long filament, and 2) a periodic train of finite filaments (at different frequencies). The development of the flow structure during the interaction is investigated. Furthermore, the drag reduction effectiveness and efficiency of the process of the interaction of the microwave filament(s) with the cylindrical shock layer for each case are studied.M.S.Includes bibliographical references (p. 71-73)
Mehka optimizacija za izbiro portfelja na osnovi vstavljenega (vgrajenega) izreka v mehko normiran linearni prostor
Get PDFBackground: This paper generalizes the results of Embedding problem of Fuzzy Number Space and its extension into a Fuzzy Banach Space C(Ω) × C(Ω), where C(Ω) is the set of all real-valued continuous functions on an open set Ω.
Objectives: The main idea behind our approach consists of taking advantage of interplays between fuzzy normed spaces and normed spaces in a way to get an equivalent stochastic program. This helps avoiding pitfalls due to severe oversimplification of the reality.
Method: The embedding theorem shows that the set of all fuzzy numbers can be embedded into a Fuzzy Banach space. Inspired by this embedding theorem, we propose a solution concept of fuzzy optimization problem which is obtained by applying the embedding function to the original fuzzy optimization problem.
Results: The proposed method is used to extend the classical Mean-Variance portfolio selection model into Mean Variance-Skewness model in fuzzy environment under the criteria on short and long term returns, liquidity and dividends.
Conclusion: A fuzzy optimization problem can be transformed into a multiobjective optimization problem which can be solved by using interactive fuzzy decision making procedure. Investor preferences determine the optimal multiobjective solution according to alternative scenarios.Ozadje: Članek posploši rezultate problema vgrajenega mehkega številskega prostora in njegovih razširitev v mehki Banachov prostor, kjer je C(Ω) množica vseh realnih kontinuirnih funkcij na odprti množici Ω.
Cilji: Poglavitna ideja v ozadju našega pristopa je izrabiti prednost medsebojnega vpliva mehkih normiranih prostorov in normiranih prostorov na način, da dobimo ekvivalenten stohastičen program. Tako se laže izognemo tveganju zaradi prevelikega poenostavljanja realnosti.
Metoda: Vgrajeni izrek pokaže, da množico vseh mehkih števil lahko vgradimo v mehki Banach-ov prostor. Izhajajoč iz tega izreka predlagamo rešitev koncepta mehkega optimizacijske problema, ki se pojavi, kadar uporabimo vgrajeno funkcijo na prvotnem mehkem optimizacijskem problemu.
Rezultati: Predlagano metodo smo uporabili, da smo razširili klasičen model (srednja varianca) za izbiro portfeja na model v mehkem okolju (srednja varianca z nesimetrično porazdelitvijo) ob kriteriju dolgoročnih in kratkoročnih dobičkov na vlaganja, likvidnosti in dividend.
Zaključek: Problem zabrisane optimizacije je mogoče pretvoriti v problem večkriterijske optimizacije, ki ga je mogoče rešiti z uporabo interaktivnega mehkega postopka odločanja. Investitorjeve preference določajo optimalno večkriterijsko rešitev glede na alternativne scenarije
Sex-specific associations of asthma acquisition with changes in DNA methylation during adolescence
Get PDFBackgroundUnderlying biological mechanisms involved in sex differences in asthma status changes from pre‐ to post‐adolescence are unclear. DNA methylation (DNAm) has been shown to be associated with the risk of asthma.ObjectiveWe hypothesized that asthma acquisition from pre‐ to post‐adolescence was associated with changes in DNAm during this period at asthma‐associated cytosine‐phosphate‐guanine (CpG) sites and such an association was sex‐specific.MethodsSubjects from the Isle of Wight birth cohort (IOWBC) with DNAm in blood at ages 10 and 18 years (n = 124 females, 151 males) were studied. Using a training‐testing approach, epigenome‐wide CpGs associated with asthma were identified. Logistic regression was used to examine sex‐specific associations of DNAm changes with asthma acquisition between ages 10 and 18 at asthma‐associated CpGs. The ALSPAC birth cohort was used for independent replication. To assess functional relevance of identified CpGs, association of DNAm with gene expression in blood was assessed.ResultsWe identified 535 CpGs potentially associated with asthma. Significant interaction effects of DNAm changes and sex on asthma acquisition in adolescence were found at 13 of the 535 CpGs in IOWBC (P‐values <1.0 × 10−3). In the replication cohort, consistent interaction effects were observed at 10 of the 13 CpGs. At 7 of these 10 CpGs, opposite DNAm changes across adolescence were observed between sexes in both cohorts. In both cohorts, cg20891917, located on IFRD1 linked to asthma, shows strong sex‐specific effects on asthma transition (P‐values <.01 in both cohorts).Conclusion and clinical relevanceGender reversal in asthma acquisition is associated with opposite changes in DNAm (males vs females) from pre‐ to post‐adolescence at asthma‐associated CpGs. These CpGs are potential biomarkers of sex‐specific asthma acquisition in adolescence.</p
Migration and having a baby
No full textThis zine emerged from an assignment in an English Language Learning and Acquisition class (ELLA 0120-001) with Douglas College instructor Tina Fusco. Students were prompted to create zines inspired by their experiences of coming to Canada and their perceptions of Canadian culture.Not peer reviewedzine
Fuzzy optimization for portfolio selection based on Embedding Theorem in Fuzzy Normed Linear Spaces
No full textBackground: This paper generalizes the results of Embedding problem of Fuzzy Number Space and its extension into a Fuzzy Banach Space C(Ω) × C(Ω), where C(Ω) is the set of all real-valued continuous functions on an open set Ω
Beyond and Behind Platforms and Algorithms: Exploring the Lived Experiences of Gig Workers
No full textWhile the literature on gig work is expanding rapidly, many are the issues that need to be answered in order to fully understand the lived experiences of gig workers and illuminate the dynamics of gig work. Despite it is widely recognized that gig workers constitute an heterogenous workforce, for instance, seminal works have focused on finding similarities among gig workers across platforms, while the mechanisms behind different gig workers’ behaviors and perceptions are still widely obscure. Moreover, most of the literature focuses on what gig workers do individually on platforms, but not – or only cursorily – on how these workers manage the interplay between their online and offline activities. Specifically, comprehending how the online dimensions of work blur or integrate with offline aspects of gig workers’ lives – such as family condition or family needs, the presence of alternative, offline jobs, the cultural context of the community and country of origin – is of significant importance. This symposium addresses these issues by examining what happens behind and beyond platforms, and by presenting four papers looking at different gig workers’ experiences and different forms of interplay between online and offline aspects of gig work.
A Multi-National Ethnography of Ride-Hailing in the Global South
Author: Lindsey Cameron; The Wharton School, U. of Pennsylvania
Author: Bobbi Thomason; Pepperdine Graziadio Business School
Understanding African Digital Platform Workers’ Behaviours through the Lens of Omoluwabi Ethos
Author: Ayomikun Idowu; U. of Sussex Business School
Gig workers and Wellbeing: How is Algorithmic Work related to Work-Life Balance?
Author: Francesca Bellesia; Dep. of Sciences and Methods for Engineering, U. of Modena and Reggio Emilia
Author: Fabiola Bertolotti; U. of Modena and Reggio Emilia
Author: Elisa Mattarelli; San Jose State U.
Gig work in organizations: Trends and perspectives from Human Resource Management professionals
Author: Ksenia Keplinger; Max Planck Institute for Intelligent Systems
Author: Aizhan Tursunbayeva; Parthenope U. of Naples
Author: Vindhya Singh; Max Planck Institute for Intelligent Systems
Author: Stefano Di Lauro; U. Mercatoru
