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Articles de revues sur le sujet « Tail approach »

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Auteur : Grafiati
Publié le 10 mars 2023

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1

Cai, Jun, et José Garrido. « A unified approach to the study of tail probabilities of compound distributions ». Journal of Applied Probability 36, no 4 (décembre 1999) : 1058–73. http://dx.doi.org/10.1239/jap/1032374755.

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We consider the tail probabilities of a class of compound distributions. First, the relations between reliability distribution classes and heavy-tailed distributions are discussed. These relations reveal that many previous results on estimating the tail probabilities are not applicable to heavy-tailed distributions.Then, a generalized Wald's identity and identities for compound geometric distributions are presented in terms of renewal processes. Using these identities, lower and upper bounds for the tail probabilities are derived in a unified way for the class of compound distributions, both under the conditions of NBU and NWU tails, which include exponential tails, as well as under the condition of heavy-tailed distributions.Finally, simplified bounds are derived by the technique of stochastic ordering. This method removes some unnecessary technical assumptions and corrects errors in the proof of some previous results.
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2

Cai, Jun, et José Garrido. « A unified approach to the study of tail probabilities of compound distributions ». Journal of Applied Probability 36, no 04 (décembre 1999) : 1058–73. http://dx.doi.org/10.1017/s0021900200017861.

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We consider the tail probabilities of a class of compound distributions. First, the relations between reliability distribution classes and heavy-tailed distributions are discussed. These relations reveal that many previous results on estimating the tail probabilities are not applicable to heavy-tailed distributions. Then, a generalized Wald's identity and identities for compound geometric distributions are presented in terms of renewal processes. Using these identities, lower and upper bounds for the tail probabilities are derived in a unified way for the class of compound distributions, both under the conditions of NBU and NWU tails, which include exponential tails, as well as under the condition of heavy-tailed distributions. Finally, simplified bounds are derived by the technique of stochastic ordering. This method removes some unnecessary technical assumptions and corrects errors in the proof of some previous results.
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3

Schwaner, M. J., S. T. Hsieh, I. Braasch, S. Bradley, C. B. Campos, C. E. Collins, C. M. Donatelli et al. « Future Tail Tales : A Forward-Looking, Integrative Perspective on Tail Research ». Integrative and Comparative Biology 61, no 2 (17 mai 2021) : 521–37. http://dx.doi.org/10.1093/icb/icab082.

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Abstract Synopsis Tails are a defining characteristic of chordates and show enormous diversity in function and shape. Although chordate tails share a common evolutionary and genetic-developmental origin, tails are extremely versatile in morphology and function. For example, tails can be short or long, thin or thick, and feathered or spiked, and they can be used for propulsion, communication, or balancing, and they mediate in predator–prey outcomes. Depending on the species of animal the tail is attached to, it can have extraordinarily multi-functional purposes. Despite its morphological diversity and broad functional roles, tails have not received similar scientific attention as, for example, the paired appendages such as legs or fins. This forward-looking review article is a first step toward interdisciplinary scientific synthesis in tail research. We discuss the importance of tail research in relation to five topics: (1) evolution and development, (2) regeneration, (3) functional morphology, (4) sensorimotor control, and (5) computational and physical models. Within each of these areas, we highlight areas of research and combinations of long-standing and new experimental approaches to move the field of tail research forward. To best advance a holistic understanding of tail evolution and function, it is imperative to embrace an interdisciplinary approach, re-integrating traditionally siloed fields around discussions on tail-related research.
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4

Zhou, Chen. « Risk Theory : A Heavy Tail Approach. » Journal of the American Statistical Association 114, no 527 (3 juillet 2019) : 1424–25. http://dx.doi.org/10.1080/01621459.2019.1662244.

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Liu, Yaolong, et Tianhong Jiang. « Conceptual Aircraft Empennage Design Based on Multidisciplinary Design Optimization Approach ». International Journal of Aerospace Engineering 2022 (18 octobre 2022) : 1–9. http://dx.doi.org/10.1155/2022/9288966.

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Within a conventional aircraft design process, the horizontal tail and vertical tail are generally sized via volume coefficient methods. In this manuscript, an improved method for conceptual aircraft tail design based on multidisciplinary design optimization (MDO) approach with stability and control constraints has been developed. To develop this method, first, the tail design requirements have been derived from the regulations and the fundamental functionalities of tail plans. Then, the empennage design is formulated as an MDO problem. Eventually the design optimization of horizontal and vertical tail is combined with the design optimization of the aircraft wing. A test case is presented for concurrent wing and tail plane design, which resulted in more than 9% reduction in aircraft block fuel weight and more than 3% reduction in aircraft maximal takeoff weight, which indicates a great potential for fuel burn and carbon reductions with empennage design optimization at conceptual aircraft design phase.
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Abraham, Deepak, Jinu Kurian Thomas, Philip Joseph et MJ Paul. « Lateral Laparoscopic Approach to Pancreatic Tail Insulinomas ». World Journal of Endocrine Surgery 4, no 1 (2012) : 3–7. http://dx.doi.org/10.5005/jp-journals-10002-1082.

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ABSTRACT Pancreatic endocrine tumors are relatively rare lesions and laparoscopic surgery is being increasingly used, especially for insulinomas because of their relatively small size and low incidence of malignancy. Laparoscopic approach to pancreatic tumors has been described in the supine position, transomentally via the lesser sac with anterior stomach retraction. We propose a simplified lateral laparoscopic approach to insulinomas localized preoperatively to the tail or distal body of pancreas. Four patients with pancreatic tail insulinomas underwent laparoscopic surgery between November 2006 and February 2008. Diagnosis was confirmed by fasting sugar, insulin and proinsulin assays. Lesions were localized by multiphasic CT scan/MRI scan and endoscopic ultrasound. All these cases had definitely identifiable enhancing lesions in the distal body/tail in relation to the splenic hilum that appeared accessible by a lateral approach. Except for the first case which was done through the traditional supine approach, the other cases were done by the lateral approach. The patients were positioned right lateral with a kidney bridge. Four subcostal ports were placed and the left colon and spleen with pancreatic tail were mobilised in the same fashion as for splenectomy or adrenalectomy. Tumors were easily identifiable corresponding to the imaging studies. Laparoscopic enucleation was successfully completed in all four patients with lesions in the tail of pancreas, one by the traditional approach and other three by the proposed lateral approach. One patient had associated splenectomy because of the proximity of the lesion to the splenic vessels. Two patients had minor pancreatic leak managed conservatively. The left lateral transperitoneal laparoscopic approach to insulinomas located in the tail of pancreas is feasible and safe. The procedure can be done with ease by surgeons who are familiar with adrenalectomy and splenectomy. How to cite this article Thomas JK, Abraham D, Joseph P, Paul MJ. Lateral Laparoscopic Approach to Pancreatic Tail Insulinomas. World J Endocr Surg 2012;4(1):3-7.
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7

Servin-Aguilar, Jesus G., Luis Rizo-Dominguez, Jorge A. Pardinas-Mir, Cesar Vargas-Rosales et Ivan Padilla-Cantoya. « Epilepsy Seizure Detection : A Heavy Tail Approach ». IEEE Access 8 (2020) : 208170–78. http://dx.doi.org/10.1109/access.2020.3038397.

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8

Asimit, Alexandru V., et Jinzhu Li. « Measuring the tail risk : An asymptotic approach ». Journal of Mathematical Analysis and Applications 463, no 1 (juillet 2018) : 176–97. http://dx.doi.org/10.1016/j.jmaa.2018.03.019.

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9

Leijen, Daan, et Anton Lorenzen. « Tail Recursion Modulo Context : An Equational Approach ». Proceedings of the ACM on Programming Languages 7, POPL (9 janvier 2023) : 1152–81. http://dx.doi.org/10.1145/3571233.

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The tail-recursion modulo cons transformation can rewrite functions that are not quite tail-recursive into a tail-recursive form that can be executed efficiently. In this article we generalize tail recursion modulo cons (TRMc) to modulo contexts (TRMC), and calculate a general TRMC algorithm from its specification. We can instantiate our general algorithm by providing an implementation of application and composition on abstract contexts, and showing that our context laws_ hold. We provide some known instantiations of TRMC, namely modulo evaluation contexts (CPS), and associative operations , and further instantiantions not so commonly associated with TRMC, such as defunctionalized evaluation contexts, monoids , semirings , exponents , and cons products . We study the modulo cons instantiation in particular and prove that an instantiation using Minamide’s hole calculus is sound. We also calculate a second instantiation in terms of the Perceus heap semantics to precisely reason about the soundness of in-place update. While all previous approaches to TRMc fail in the presence of non-linear control (for example induced by call/cc, shift/reset or algebraic effect handlers), we can elegantly extend the heap semantics to a hybrid approach which dynamically adapts to non-linear control flow. We have a full implementation of hybrid TRMc in the Koka language and our benchmark shows the TRMc transformed functions are always as fast or faster than using manual alternatives.
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10

Schäfer, Dominik. « T-tail flutter simulations with regard to quadratic mode shape components ». CEAS Aeronautical Journal 12, no 3 (18 juin 2021) : 621–32. http://dx.doi.org/10.1007/s13272-021-00524-8.

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AbstractIt is known that the dynamic aeroelastic stability of T-tails is dependent on the steady aerodynamic forces at aircraft trim condition. Accounting for this dependency in the flutter solution process involves correction methods for doublet lattice method (DLM) unsteady aerodynamics, enhanced DLM algorithms, unsteady vortex lattice methods (UVLM), or the use of CFD. However, the aerodynamic improvements along with a commonly applied modal approach with linear displacements results in spurious stiffness terms, which distort the flutter velocity prediction. Hence, a higher order structural approach with quadratic mode shape components is required for accurate flutter velocity prediction of T-tails. For the study of the effects of quadratic mode shape components on T-tail flutter, a generic tail configuration without sweep and taper is used. Euler based CFD simulations are applied involving a linearized frequency domain (LFD) approach to determine the generalized aerodynamic forces. These forces are obtained based on steady CFD computations at varying horizontal tail plane (HTP) incidence angles. The quadratic mode shape components of the fundamental structural modes for the vertical tail plane (VTP), i.e., out-of-plane bending and torsion, are received from nonlinear as well as linear finite element analyses. Modal coupling resulting solely from the extended modal representation of the structure and its influence on T-tail flutter is studied. The g-method is applied to solve for the flutter velocities and corresponding flutter mode shapes. The impact of the quadratic mode shape components is visualized in terms of flutter velocities in dependency of the HTP incidence angle and the static aerodynamic HTP loading.
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11

Viscardi, Abbie V., et Patricia Turner. « 12 A multimodal approach for piglet pain management after tail docking ». Journal of Animal Science 97, Supplement_2 (juillet 2019) : 6–7. http://dx.doi.org/10.1093/jas/skz122.011.

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Abstract Millions of piglets on commercial production farms are tail docked each year to reduce the incidence of tail biting. While this procedure is known to be painful, piglets in the United States are often not provided analgesia or anesthesia for pain relief. The objectives of this study were to assess a multimodal approach to managing tail docking pain in piglets, using 0.4 mg/kg meloxicam (MEL), 0.04 mg/kg buprenorphine (BUP), and Maxilene® (MAX). The effectiveness of each drug and drug combination was evaluated using behavioral indicators, vocalization, and facial grimace analysis. This study also assessed whether male and female piglets responded differently to pain or pain treatments. Four-day-old piglets from 14 litters (n = 165 total) were used and piglets within a litter were randomly assigned to one of six possible treatments: MEL, BUP, MEL + BUP, MEL + BUP + MAX, no treatment (tail docked control), or sham (non-tail docked control). Treatments were administered intramuscularly (MEL, BUP) or topically on the tail (MAX) 20 min prior to tail docking. Piglets administered MEL + BUP and BUP demonstrated significantly fewer pain behaviors than piglets in the MEL and no treatment group (p < 0.05). MEL + BUP + MAX and BUP piglets also grimaced significantly less than piglets in the no treatment group (p < 0.05). There were no significant differences in emitted vocalizations between the analgesia-treated piglets and the no treatment group, and both injection and tail docking elicited piglet vocalizations of similar frequency, power, and energy (P > 0.05). There were no significant differences in behavior, facial grimacing or emitted vocalizations between male and female piglets. All treatment groups with buprenorphine were able to alleviate tail docking-associated pain, suggesting that opioid administration is highly effective for managing piglet pain.
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12

Heim, Steve W., Mostafa Ajallooeian, Peter Eckert, Massimo Vespignani et Auke Jan Ijspeert. « On designing an active tail for legged robots : simplifying control via decoupling of control objectives ». Industrial Robot : An International Journal 43, no 3 (16 mai 2016) : 338–46. http://dx.doi.org/10.1108/ir-10-2015-0190.

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Purpose The purpose of this paper is to explore the possible roles of active tails for steady-state legged locomotion, focusing on a design principle which simplifies control by decoupling different control objectives. Design/methodology/approach A series of simple models are proposed which capture the dynamics of an idealized running system with an active tail. These models suggest that the overall control problem can be simplified and effectively decoupled via a proper tail design. This design principle is further explored in simulation using trajectory optimization. The results are then validated in hardware using a one degree-of-freedom active tail mounted on the quadruped robot Cheetah-Cub. Findings The results of this paper show that an active tail can greatly improve both forward velocity and reduce body-pitch per stride while adding minimal complexity. Further, the results validate the design principle of using long, light tails compared to shorter heavier ones. Originality/value This paper builds on previous results, with a new focus on steady-state locomotion and in particular deals directly with stance phase dynamics. A novel design principle for tails is proposed and validated.
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Pertaia, Giorgi, et Stan Uryasev. « Fitting heavy-tailed mixture models with CVaR constraints ». Dependence Modeling 7, no 1 (18 novembre 2019) : 365–74. http://dx.doi.org/10.1515/demo-2019-0019.

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AbstractStandard methods of fitting finite mixture models take into account the majority of observations in the center of the distribution. This paper considers the case where the decision maker wants to make sure that the tail of the fitted distribution is at least as heavy as the tail of the empirical distribution. For instance, in nuclear engineering, where probability of exceedance (POE) needs to be estimated, it is important to fit correctly tails of the distributions. The goal of this paper is to supplement the standard methodology and to assure an appropriate heaviness of the fitted tails. We consider a new Conditional Value-at-Risk (CVaR) distance between distributions, that is a convex function with respect to weights of the mixture. We have conducted a case study demonstrating e˚ciency of the approach. Weights of mixture are found by minimizing CVaR distance between the mixture and the empirical distribution. We have suggested convex constraints on weights, assuring that the tail of the mixture is as heavy as the tail of empirical distribution.
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Büttner, Kathrin, Irena Czycholl, Heidi Basler et Joachim Krieter. « Effects of an intensified human–animal interaction on tail biting in pigs during the rearing period ». Journal of Agricultural Science 156, no 8 (octobre 2018) : 1039–46. http://dx.doi.org/10.1017/s002185961800103x.

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AbstractTail biting in pigs is a serious welfare problem with multifactorial causes. Several risk factors are described in the literature ranging from environmental factors including stocking densities, deficiencies in feed quality or accessibility, to internal factors such as poor health status, genetics or sex. Also, the human–animal relationship can have an effect on behaviour and performance of the animals. Thus, the aim of the current study was to evaluate whether intensified human–animal interaction in the rearing period can reduce the occurrence of tail biting in weaned piglets. For this, two treatment groups were established. The trial group differed only in intensified human–animal interaction (e.g. calm speech, petting, food provision) from the control group, which was carried out three times a week by one person for 15 min in each pen. Once a week the animals’ tails were scored regarding tail lesions and losses and a human approach test was performed. The intensified human–animal interaction influenced the animals’ behaviour towards the human as well as towards their pen mates. The trial group showed significantly better results compared with the control group, i.e. fewer tail lesions and more animals with intact tails. Also, the results of the human approach test in the trial group showed a lower latency to approach compared with the control group. Thus, integration of an intensified human–animal interaction into the daily practice of pig farms could be one possibility for enhancing the human–animal relationship and reducing occurrence of tail biting.
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Dai, Shuanping, et Markus Taube. « The long tail thesis ». Chinese Management Studies 14, no 2 (21 novembre 2019) : 433–54. http://dx.doi.org/10.1108/cms-03-2019-0109.

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Purpose This paper aims to explore the functionality of long tail markets (LTM), where the consumers cannot be reached or are ignored by the traditional mainstream businesses, in new products and business development. Design/methodology/approach First, the authors review two Chinese entrepreneurial practices in the Fintech sector and low-speed electric vehicles (LSEV) and describe their stylized facts; second, they explore a possible theoretical LTM framework to underscore these practices; third, they make a connection between LTM and existing business models and analyze its significance and practical implications in business, in particular, in developing economies. Findings The LTM business approach has helped Chinese companies in the Fintech sector and LSEVs gain global attention. The success factors of LTM for businesses are identifying a specific customer base, being aware of localization products and playing skillfully with regulations; the LTM approach has several overlaps with existing studies on niche products and base of the pyramid market. Originality/value Based on some emerging and attractive business practices in China, this paper offers a valuable attempt to theorize them as long tail phenomenon. The LTM thesis provides a potential framework to reference for similar methods elsewhere and may illuminate entrepreneurship to be explored in similar markets.
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Voracek, Martin, Elisabeth Mohr et Michael Hagmann. « On the Importance of Tail Ratios for Psychological Science ». Psychological Reports 112, no 3 (juin 2013) : 872–86. http://dx.doi.org/10.2466/03.pr0.112.3.872-886.

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Even small group-mean differences (whether combined with variance differences or not) or variance differences alone (absent mean differences) can generate marked and sometimes surprising imbalances in the representation of the respective groups compared in the distributional tail regions. Such imbalances in group representation, quantified as tail ratios, have general importance in the context of any threshold, susceptibility, diathesis-stress, selection, or similar models (including the study of sex differences), as widely conceptualized and applied in the psychological, social, medical, and biological sciences. However, commonly used effect-size measures, such as Cohen's d, largely exploit data information around the center of distributions, rather than from the tails, thereby missing potentially important patterns found in the tail regions. This account reviews the background and history of tail ratios, emphasizes their importance for psychological research, proposes a consensus approach for defining and interpreting them, introduces a tail-ratio calculator, and outlines future research agenda.
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17

Ranjani, C., et Anita Kumar. « Long tail vs. blockbusters - a data-driven approach ». International Journal of Business and Systems Research 11, no 1/2 (2017) : 118. http://dx.doi.org/10.1504/ijbsr.2017.080844.

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Ranjani, C., et Anita Kumar. « Long tail vs. blockbusters - a data-driven approach ». International Journal of Business and Systems Research 11, no 1/2 (2017) : 118. http://dx.doi.org/10.1504/ijbsr.2017.10000881.

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19

Li, Haijun, et Peiling Wu. « Extremal dependence of copulas : A tail density approach ». Journal of Multivariate Analysis 114 (février 2013) : 99–111. http://dx.doi.org/10.1016/j.jmva.2012.07.005.

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Di Bernardino, Elena, Véronique Maume-Deschamps et Clémentine Prieur. « Estimating a bivariate tail : A copula based approach ». Journal of Multivariate Analysis 119 (août 2013) : 81–100. http://dx.doi.org/10.1016/j.jmva.2013.03.020.

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21

Liu, Bin, Cheng Zhou et Xinsheng Zhang. « A tail adaptive approach for change point detection ». Journal of Multivariate Analysis 169 (janvier 2019) : 33–48. http://dx.doi.org/10.1016/j.jmva.2018.08.010.

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22

Ramu, Palaniappan, Nam H. Kim et Raphael T. Haftka. « Multiple tail median approach for high reliability estimation ». Structural Safety 32, no 2 (mars 2010) : 124–37. http://dx.doi.org/10.1016/j.strusafe.2009.09.002.

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Kuras, Tautvydas, Jonas Sprindys et Jonas Šiaulys. « Martingale Approach to Derive Lundberg-Type Inequalities ». Mathematics 8, no 10 (11 octobre 2020) : 1742. http://dx.doi.org/10.3390/math8101742.

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In this paper, we find the upper bound for the tail probability Psupn⩾0∑I=1nξI>x with random summands ξ1,ξ2,… having light-tailed distributions. We find conditions under which the tail probability of supremum of sums can be estimated by quantity ϱ1exp{−ϱ2x} with some positive constants ϱ1 and ϱ2. For the proof we use the martingale approach together with the fundamental Wald’s identity. As the application we derive a few Lundberg-type inequalities for the ultimate ruin probability of the inhomogeneous renewal risk model.
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Zhuang, De Dong. « Tail Dependence Structure between Carbon Emission Allowances Returns Based on Copulas ». Applied Mechanics and Materials 397-400 (septembre 2013) : 726–30. http://dx.doi.org/10.4028/www.scientific.net/amm.397-400.726.

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This paper has focus on analyzing tail dependence structure between EUA spots returns and futures returns based on copula approach, which EUA spots negotiated on BlueNext and futures negotiated on European Climate Exchange within the European Union Emission Trading Scheme (EU ETS) during the Phase II. According to the generalized Pareto distribution (GPD) and different Copula functions, the research shows that Gumbel Copula based on the GPD marginal distribution can indicate the tail dependence structure of EUA spots returns and futures returns accurately, i.e. the dependence between upper-tails of EUA spot and Dec10 is stronger than that of lower-tails of them. In other words, EUA spots and futures are more likely to soar together than slump together during the Phase II.
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Messaoud, Samia Ben, et Mondher Kouki. « Dependence Structure between Conventional and Islamic Indexes : A Copula Approach ». International Journal of Islamic Banking and Finance Research 4, no 2 (9 août 2020) : 22–30. http://dx.doi.org/10.46281/ijibfr.v4i2.703.

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This article examines the conditional dependence structure between Islamic stock indexes and conventional counterparts. Our empirical analysis relies on Islamic and conventional indexes of dependence distribution using copula methods over the period 1999–2014. The results from the copula models denote that the dependence is not formally symmetric in that the lower tail dependence is significantly larger than the upper tail dependence.
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Bracke, MBM. « Rope test may indicate efficacy of tail-biting treatments in growing pigs ». Animal Welfare 18, no 3 (août 2009) : 263–66. http://dx.doi.org/10.1017/s0962728600000518.

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AbstractTail biting is a most serious welfare problem in pigs raised for slaughter. In instances of an outbreak of tail biting, scientists have recommended that farmers take measures such as removal of affected animals, provision of enrichment materials and application of repellents to the pigs’ tails. However, no scientific study has ever confirmed the efficacy of any of these suggestions in counteracting an ongoing outbreak. Here, the efficacy of two repellent ointments, Dippel's oil and Stockholm tar, were examined in a tail-chew test. For this, a novel piece of nylon rope was used as a tail model to measure biting behaviour semi-automatically in 24 single-sex groups of growing pigs (total 264 pigs). Repeated measures analysis showed no effect of time, gender or unit (12 pens per unit), but a highly significant effect of treatment, in that both Stockholm tar and Dippel's oil significantly reduced rope manipulation compared to controls. These results suggest that Stockholm tar and Dippel's oil may be effective in reducing tail biting. The approach taken may be valuable in further testing of strategies to reduce tail biting and improving pig welfare.
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Ramm, Till, Emily J. Roycroft et Johannes Müller. « Convergent evolution of tail spines in squamate reptiles driven by microhabitat use ». Biology Letters 16, no 2 (février 2020) : 20190848. http://dx.doi.org/10.1098/rsbl.2019.0848.

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The repeated evolution of convergent or analogous traits is often used as evidence for adaptive evolution. Squamate reptiles show a high degree of convergence in a variety of morphological traits; however, the evolutionary mechanisms driving these patterns are not fully understood. Here, we investigate the evolution of tail spines, a trait that evolved multiple times in evolutionarily independent clades of lizards. Taking a comparative phylogenetic approach, we use 2877 squamate species to demonstrate that the evolution of spiny tails is correlated with microhabitat use, with species that live in rocky habitats significantly more likely to have evolved spiny tails. In the light of previous behavioural observations, our results suggest that spiny-tailed lizards have an advantage in rocky habitats through predation avoidance, where tail spines are used to prevent extraction from rocky crevices. In concordance with previous research on lizard body armour, our results suggest that the evolution of tail spines is coupled to both a rock-dwelling lifestyle and predator avoidance strategies, and highlight a complex interplay between different selective pressures on the evolution of defensive morphologies in reptiles.
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Yamagami, Sayuri, Yohei Okada, Yoshikazu Kitano et Kazuhiro Chiba. « Peptide Head‐to‐Tail Cyclization : A “Molecular Claw” Approach ». European Journal of Organic Chemistry 2021, no 22 (4 mai 2021) : 3133–38. http://dx.doi.org/10.1002/ejoc.202100185.

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Božović, Miloš. « Portfolio Tail Risk : A Multivariate Extreme Value Theory Approach ». Entropy 22, no 12 (17 décembre 2020) : 1425. http://dx.doi.org/10.3390/e22121425.

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This paper develops a method for assessing portfolio tail risk based on extreme value theory. The technique applies separate estimations of univariate series and allows for closed-form expressions for Value at Risk and Expected Shortfall. Its forecasting ability is tested on a portfolio of U.S. stocks. The in-sample goodness-of-fit tests indicate that the proposed approach is better suited for portfolio risk modeling under extreme market movements than comparable multivariate parametric methods. Backtesting across multiple quantiles demonstrates that the model cannot be rejected at any reasonable level of significance, even when periods of stress are included. Numerical simulations corroborate the empirical results.
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Piccino, M., R. Palumbo, G. Pirozzolo, L. D'Alimonte, M. Bonfiglio, M. Rizzo, S. Ramuscello et A. G. Recordare. « Tailored laparoscopic approach for pancreatic tail resection for cancer ». HPB 23 (2021) : S1016—S1017. http://dx.doi.org/10.1016/j.hpb.2021.08.767.

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Cortese, Federico Pasquale. « Tail Dependence in Financial Markets : A Dynamic Copula Approach ». Risks 7, no 4 (11 novembre 2019) : 116. http://dx.doi.org/10.3390/risks7040116.

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This article is concerned with the study of the tail correlation among equity indices by means of dynamic copula functions. The main idea is to consider the impact of the use of copula functions in the accuracy of the model’s parameters and in the computation of Value-at-Risk (VaR). Results show that copulas provide more sophisticated results in terms of the accuracy of the forecasted VaR, in particular, if they are compared with the results obtained from Dynamic Conditional Correlation (DCC) model.
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Mariani, Leonardo, Mauro Pezze et Mauro Santoro. « GK-Tail+ An Efficient Approach to Learn Software Models ». IEEE Transactions on Software Engineering 43, no 8 (1 août 2017) : 715–38. http://dx.doi.org/10.1109/tse.2016.2623623.

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Politis, Dimitris N. « A new approach on estimation of the tail index ». Comptes Rendus Mathematique 335, no 3 (janvier 2002) : 279–82. http://dx.doi.org/10.1016/s1631-073x(02)02450-0.

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Su, Jianxi, et Lei Hua. « A general approach to full-range tail dependence copulas ». Insurance : Mathematics and Economics 77 (novembre 2017) : 49–64. http://dx.doi.org/10.1016/j.insmatheco.2017.08.009.

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35

Jin, Xisong, et Francisco de A. Nadal De Simone. « Banking systemic vulnerabilities : A tail-risk dynamic CIMDO approach ». Journal of Financial Stability 14 (octobre 2014) : 81–101. http://dx.doi.org/10.1016/j.jfs.2013.12.004.

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Echaust, Krzysztof, et Małgorzata Just. « Value at Risk Estimation Using the GARCH-EVT Approach with Optimal Tail Selection ». Mathematics 8, no 1 (11 janvier 2020) : 114. http://dx.doi.org/10.3390/math8010114.

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A conditional Extreme Value Theory (GARCH-EVT) approach is a two-stage hybrid method that combines a Generalized Autoregressive Conditional Heteroskedasticity (GARCH) filter with the Extreme Value Theory (EVT). The approach requires pre-specification of a threshold separating distribution tails from its middle part. The appropriate choice of a threshold level is a demanding task. In this paper we use four different optimal tail selection algorithms, i.e., the path stability method, the automated Eye-Ball method, the minimization of asymptotic mean squared error method and the distance metric method with a mean absolute penalty function, to estimate out-of-sample Value at Risk (VaR) forecasts and compare them to the fixed threshold approach. Unlike other studies, we update the optimal fraction of the tail for each rolling window of the returns. The research objective is to verify to what extent optimization procedures can improve VaR estimates compared to the fixed threshold approach. Results are presented for a long and a short position applying 10 world stock indices in the period from 2000 to June 2019. Although each approach generates different threshold levels, the GARCH-EVT model produces similar Value at Risk estimates. Therefore, no improvement of VaR accuracy may be observed relative to the conservative approach taking the 95th quantile of returns as a threshold.
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Nguyen, Tilo, et Gennady Samorodnitsky. « MULTIVARIATE TAIL ESTIMATION WITH APPLICATION TO ANALYSIS OF COVAR ». ASTIN Bulletin 43, no 2 (mai 2013) : 245–70. http://dx.doi.org/10.1017/asb.2013.13.

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AbstractThe quality of estimation of multivariate tails depends significantly on the portion of the sample included in the estimation. A simple approach involving sequential statistical testing is proposed in order to select which observations should be used for estimation of the tail and spectral measures. We prove that the estimator is consistent. We test the proposed method on simulated data, and subsequently apply it to analyze CoVaR for stock and index returns.
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Paolo Natale, Francesco. « Optimisation in the presence of tail-dependence and tail risk : A heuristic approach for strategic asset allocation ». Journal of Asset Management 8, no 6 (28 janvier 2008) : 374–400. http://dx.doi.org/10.1057/palgrave.jam.2250083.

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Sarkar, Abhigyan, Juhi Gahlot Sarkar, Sreejesh S. et Anusree M.R. « A qualitative investigation of e-tail brand affect ». Marketing Intelligence & ; Planning 36, no 3 (8 mai 2018) : 365–80. http://dx.doi.org/10.1108/mip-09-2017-0198.

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Purpose The purpose of this paper is to qualitatively investigate various factors associated with e-tail store brand affect. Design/methodology/approach Data were collected by conducting semi-structured depth interviews following a storytelling approach. The data were coded using the grounded theory method. Findings Data analysis shows that anticipated service recovery, deal attractiveness and luxury e-tail brand image predict e-tail store brand affect. These predictors play their roles under the moderating influences of specific moderators. The desirable marketing outcomes of e-tail store brand affect are e-tail branded app usage, spreading positive word of mouth and secure attachment style toward e-tailer. Originality/value The value of this study lies in developing a grounded theory based causal process model that can provide managerial insights on how to enhance e-tail brand affect.
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Pacáková, Viera, et Pavla Jindrová. « Simulation of Extreme Insured Losses in Natural Catastrophes ». PROOF 1 (7 avril 2021) : 32–36. http://dx.doi.org/10.37394/232020.2021.1.5.

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This article aims to present the application of probability modelling and simulations based on quantile function of extreme insured losses in the world natural catastrophes based on data in time period 1970-2014, published in Swiss Re Sigma No2/2015. Quantile function provides an appropriate and flexible approach to the probability modelling needed to obtain well-fitted tails. We are specifically interested in modelling and simulations the tails of loss distributions. In a number of applications of quantile functions in insurance and reinsurance risk management interest focuses particularly on the extreme observations in the upper tail of probability distribution. Fortunately it is possible to simulate the observations in one tail of distribution without simulating the central values. This advantage will be used for estimate a few extreme high insured losses in the world’s natural catastrophes in future.
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Goovaerts, Marc J., Rob Kaas, Jan Dhaene et Qihe Tang. « A Unified Approach to Generate Risk Measures ». ASTIN Bulletin 33, no 02 (novembre 2003) : 173–91. http://dx.doi.org/10.2143/ast.33.2.503689.

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The paper derives many existing risk measures and premium principles by minimizing a Markov bound for the tail probability. Our approach involves two exogenous functions v(S) and φ(S, π) and another exogenous parameter α ≤ 1. Minimizing a general Markov bound leads to the following unifying equation: E [φ (S, π)] = αE [v (S)]. For any random variable, the risk measure π is the solution to the unifying equation. By varying the functions φ and v, the paper derives the mean value principle, the zero-utility premium principle, the Swiss premium principle, Tail VaR, Yaari's dual theory of risk, mixture of Esscher principles and more. The paper also discusses combining two risks with super-additive properties and sub-additive properties. In addition, we recall some of the important characterization theorems of these risk measures.
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Goovaerts, Marc J., Rob Kaas, Jan Dhaene et Qihe Tang. « A Unified Approach to Generate Risk Measures ». ASTIN Bulletin 33, no 2 (novembre 2003) : 173–91. http://dx.doi.org/10.1017/s0515036100013428.

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The paper derives many existing risk measures and premium principles by minimizing a Markov bound for the tail probability. Our approach involves two exogenous functions v(S) and φ(S, π) and another exogenous parameter α ≤ 1. Minimizing a general Markov bound leads to the following unifying equation: E [φ (S, π)] = αE [v (S)].For any random variable, the risk measure π is the solution to the unifying equation. By varying the functions φ and v, the paper derives the mean value principle, the zero-utility premium principle, the Swiss premium principle, Tail VaR, Yaari's dual theory of risk, mixture of Esscher principles and more. The paper also discusses combining two risks with super-additive properties and sub-additive properties. In addition, we recall some of the important characterization theorems of these risk measures.
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Viscardi, AV, et PV Turner. « Use of meloxicam, buprenorphine, and Maxilene® to assess a multimodal approach for piglet pain management, part 2 : tail-docking ». Animal Welfare 28, no 4 (1 novembre 2019) : 499–510. http://dx.doi.org/10.7120/09627286.28.4.499.

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Piglets on commercial pig farms are often tail-docked to reduce the incidence of tail-biting. While this is a painful procedure, piglets are often not provided analgesia or anaesthesia for pain relief. The objectives of this study were to assess a multimodal approach to managing tail-docking pain in piglets, using 0.4 mg kg–1 meloxicam (MEL), 0.04 mg kg–1 buprenorphine (BUP), and Maxilene® (MAX), a topical anaesthetic. The effectiveness of each drug and drug combination was evaluated using behavioural indicators, vocalisation, and facial grimace analysis. This study also assessed whether male and female piglets responded differently to pain or pain treatments. Piglets were randomly assigned to one of six possible treatments: MEL, BUP, MEL + BUP, MEL + BUP + MAX, no treatment (tail-docked control), or sham (non-tail-docked control). Vocalisations were recorded at initial handling, injection, and tail-docking. Piglets administered MEL + BUP and BUP demonstrated significantly fewer pain behaviours than piglets in the MEL and no treatment group. MEL + BUP + MAX and BUP piglets displayed significantly lower facial grimace scores than piglets in the no treatment group. There were no significant differences in emitted vocalisations between the analgesia-treated piglets and the no treatment group and both injection and tail-docking elicited piglet vocalisations of similar frequency, power, and energy. There were no significant differences in behaviour, facial grimacing or emitted vocalisations between male and female piglets. All treatment groups with buprenorphine were able to alleviate tail-docking-associated pain, suggesting that opioid administration is highly effective for managing piglet pain.
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Tijms, Henk C., et Michel C. T. Van De Coevering. « A Simple Numerical Approach for Infinite-State Markov Chains ». Probability in the Engineering and Informational Sciences 5, no 3 (juillet 1991) : 285–95. http://dx.doi.org/10.1017/s0269964800002096.

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This paper presents a simple and practical approach to solving the equilibrium equations for a class of Markov chains with an infinite number of states. Markov chains arising in queueing and inventory applications often have the property that the state probabilities exhibit a geometric tail behavior. The basic idea of the approach is to reduce the infinite system of linear equations to a finite system using the geometric tail behavior of the equilibrium probabilities. The reduction typically leads to a remarkably small system of linear equations that can be routinely solved by a Gaussian elimination method. An application is given to the single-server queue with scheduled arrivals.
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Miyazawa, Masakiyo. « Martingale approach for tail asymptotic problems in the gener­alized Jackson network ». Probability and Mathematical Statistics 37, no 2 (14 mai 2018) : 395–430. http://dx.doi.org/10.19195/0208-4147.37.2.11.

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MARTINGALE APPROACH FOR TAIL ASYMPTOTIC PROBLEMS IN THE GENERALIZED JACKSON NETWORKWe study the tail asymptotic of the stationary joint queue length distribution for a generalized Jackson network GJN for short, assumingits stability. For the two-station case, this problem has recently been solved in the logarithmic sense for the marginal stationary distributions under the setting that arrival processes and service times are of phase-type. In this paper, we study similar tail asymptotic problems on the stationary distribution, but problems and assumptions are different. First, the asymptotics are studied not only for the marginal distribution but also the stationary probabilities of state sets of small volumes. Second, the interarrival and service times are generally distributed and light tailed, but of phase-type in some cases. Third, we also study the case that there are more than two stations, although the asymptotic results are less complete. For them, we develop a martingale method, which has been recently applied to a single queue with many servers by the author.
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Ledford, Anthony W., et Jonathan A. Tawn. « Concomitant tail behaviour for extremes ». Advances in Applied Probability 30, no 1 (mars 1998) : 197–215. http://dx.doi.org/10.1239/aap/1035228000.

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The influence of bivariate extremal dependence on the limiting behaviour of the concomitant of the largest order statistic is examined. Our approach is to fix the marginal distributions and derive a general tail characterisation of the joint survivor function. From this, we identify the normalisation required to obtain the limiting distribution of the concomitant of the largest order statistic, obtain its tail form, and investigate the limiting probability that the vector of componentwise maxima occurs as an observation of the bivariate process. The results are illustrated for a range of extremal dependence forms.
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Ledford, Anthony W., et Jonathan A. Tawn. « Concomitant tail behaviour for extremes ». Advances in Applied Probability 30, no 01 (mars 1998) : 197–215. http://dx.doi.org/10.1017/s0001867800008168.

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The influence of bivariate extremal dependence on the limiting behaviour of the concomitant of the largest order statistic is examined. Our approach is to fix the marginal distributions and derive a general tail characterisation of the joint survivor function. From this, we identify the normalisation required to obtain the limiting distribution of the concomitant of the largest order statistic, obtain its tail form, and investigate the limiting probability that the vector of componentwise maxima occurs as an observation of the bivariate process. The results are illustrated for a range of extremal dependence forms.
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UENO, Akira, et Haeng-Nam KO. « New Fractographic Approach for Alumina Ceramics with Pore Tail Method. » Transactions of the Japan Society of Mechanical Engineers Series A 62, no 595 (1996) : 686–91. http://dx.doi.org/10.1299/kikaia.62.686.

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Abbasi, Babak, et S. Zahra Hosseinifard. « Tail conditional expectation for multivariate distributions : A game theory approach ». Statistics & ; Probability Letters 83, no 10 (octobre 2013) : 2228–35. http://dx.doi.org/10.1016/j.spl.2013.06.012.

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Mirhosseini, Amirhossein, et Thomas F. Wenisch. « The Queuing-First Approach for Tail Management of Interactive Services ». IEEE Micro 39, no 4 (1 juillet 2019) : 55–64. http://dx.doi.org/10.1109/mm.2019.2897671.

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