bound constraints
Recently Published Documents


TOTAL DOCUMENTS

155
(FIVE YEARS 36)

H-INDEX

19
(FIVE YEARS 4)

Mathematics ◽  
2022 ◽  
Vol 10 (2) ◽  
pp. 270
Author(s):  
Chenyang Hu ◽  
Yuelin Gao ◽  
Fuping Tian ◽  
Suxia Ma

Quadratically constrained quadratic programs (QCQP), which often appear in engineering practice and management science, and other fields, are investigated in this paper. By introducing appropriate auxiliary variables, QCQP can be transformed into its equivalent problem (EP) with non-linear equality constraints. After these equality constraints are relaxed, a series of linear relaxation subproblems with auxiliary variables and bound constraints are generated, which can determine the effective lower bound of the global optimal value of QCQP. To enhance the compactness of sub-rectangles and improve the ability to remove sub-rectangles, two rectangle-reduction strategies are employed. Besides, two ϵ-subproblem deletion rules are introduced to improve the convergence speed of the algorithm. Therefore, a relaxation and bound algorithm based on auxiliary variables are proposed to solve QCQP. Numerical experiments show that this algorithm is effective and feasible.


Algorithms ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 325
Author(s):  
Lanfen Liu ◽  
Xinfeng Yang

The characteristics of railway dangerous goods accidents are very complex. The rescue of railway dangerous goods accidents should consider the timeliness of rescue, the uncertainty of traffic environment and the diversity of rescue resources. Thus, the purpose of this paper is to confront the rescue resources scheduling problem of railway dangerous goods accident by considering factors such as rescue capacity, rescue demand and response time. Based on the analysis of travel time and reliability for rescue route, a multi-objective scheduling model of rescue resources based on travel time reliability is constructed in order to minimize the total arrival time of rescue resources and to maximize total reliability. The proposed model is more reliable than the traditional model due to the consideration of travel time reliability of rescue routes. Moreover, a two-stage algorithm is designed to solve this problem. A multi-path algorithm with bound constraints is used to obtain the set of feasible rescue routes in the first stage, and the NSGA-II algorithm is used to determine the scheduling of rescue resources for each rescue center. Finally, the two-stage algorithm is tested on a regional road network, and the results show that the designed two-stage algorithm is valid for solving the rescue resource scheduling problem of dangerous goods accidents and is able to obtain the rescue resource scheduling scheme in a short period of time.


2021 ◽  
Author(s):  
Jeremie Giraud ◽  
Hoël Seillé ◽  
Mark D. Lindsay ◽  
Gerhard Visser ◽  
Vitaliy Ogarko ◽  
...  

Abstract. We propose, test and apply a methodology integrating 1D magnetotelluric (MT) and magnetic data inversion, with a focus on the characterization of the cover-basement interface. It consists of a cooperative inversion workflow relying on standalone inversion codes. Probabilistic information about the presence of rock units is derived from MT and passed on to magnetic inversion through constraints combining such structural constraints with petrophysical prior information. First, we perform the 1D probabilistic inversion of MT data for all sites and recover the respective probabilities of observing the cover-basement interface, which we interpolate to the rest of the study area. We then calculate the probabilities of observing the different rock units and partition the model into domains defined by combinations of rock units with non-zero probabilities. Third, we combine such domains with petrophysical information to apply spatially-varying, disjoint interval bound constraints to least-squares magnetic data inversion. We demonstrate the proof-of-concept using a realistic synthetic model reproducing features from the Mansfield area (Victoria, Australia) using a series of uncertainty indicators. We then apply the workflow to field data from the prospective mining region of Cloncurry (Queensland, Australia). Results indicate that our integration methodology efficiently leverages the complementarity between separate MT and magnetic data modelling approaches and can improve our capability to image the cover-basement interface. In the field application case, our findings also suggest that the proposed workflow may be useful to refine existing geological interpretations and to infer lateral variations within the basement.


2021 ◽  
Vol 14 (11) ◽  
pp. 6681-6709
Author(s):  
Jérémie Giraud ◽  
Vitaliy Ogarko ◽  
Roland Martin ◽  
Mark Jessell ◽  
Mark Lindsay

Abstract. The quantitative integration of geophysical measurements with data and information from other disciplines is becoming increasingly important in answering the challenges of undercover imaging and of the modelling of complex areas. We propose a review of the different techniques for the utilisation of structural, petrophysical, and geological information in single physics and joint inversion as implemented in the Tomofast-x open-source inversion platform. We detail the range of constraints that can be applied to the inversion of potential field data. The inversion examples we show illustrate a selection of scenarios using a realistic synthetic data set inspired by real-world geological measurements and petrophysical data from the Hamersley region (Western Australia). Using Tomofast-x's flexibility, we investigate inversions combining the utilisation of petrophysical, structural, and/or geological constraints while illustrating the utilisation of the L-curve principle to determine regularisation weights. Our results suggest that the utilisation of geological information to derive disjoint interval bound constraints is the most effective method to recover the true model. It is followed by model smoothness and smallness conditioned by geological uncertainty and cross-gradient minimisation.


2021 ◽  
Vol 43 (3) ◽  
pp. 1-51
Author(s):  
Graeme Gange ◽  
Zequn Ma ◽  
Jorge A. Navas ◽  
Peter Schachte ◽  
Harald Søndergaard ◽  
...  

Zones and Octagons are popular abstract domains for static program analysis. They enable the automated discovery of simple numerical relations that hold between pairs of program variables. Both domains are well understood mathematically but the detailed implementation of static analyses based on these domains poses many interesting algorithmic challenges. In this article, we study the two abstract domains, their implementation and use. Utilizing improved data structures and algorithms for the manipulation of graphs that represent difference-bound constraints, we present fast implementations of both abstract domains, built around a common infrastructure. We compare the performance of these implementations against alternative approaches offering the same precision. We quantify the differences in performance by measuring their speed and precision on standard benchmarks. We also assess, in the context of software verification, the extent to which the improved precision translates to better verification outcomes. Experiments demonstrate that our new implementations improve the state of the art for both Zones and Octagons significantly.


Author(s):  
Anthony Foy

After historicizing the politics of racial representation in the slave narrative, this article considers how race, gender, and class intersect historically in the autobiographical production of Black men in the United States. At the dawn of the Jim Crow era, Black autobiography conformed to a cultural politics of racial synecdoche, which avowed that racial progress depended on the respectability of esteemed individuals. Dominated by aspirational figures who presented themselves as racial emblems, Black autobiography became closely aligned with the imperatives of Black middle-class formation, actuating a discrete form of racial publicity that erected disciplinary boundaries around Black self-presentation and silenced disreputable figures. With the emergence of criminal and sexual self-reference, whether subtle or striking, in the narratives of Black men, autobiographers like boxer Jack Johnson, scholar J. Saunders Redding, and writer Claude Brown, disrupted the class-bound constraints that had determined Black autobiographical production, staging an internecine class struggle over the terms of racial representation—that is, between contending discourses of racial respectability and racial authenticity


Target ◽  
2021 ◽  
Author(s):  
Biyu (Jade) Du

Abstract This article examines how the voices of trial participants are mediated by court interpreters. The research focuses on closing statements articulated by defendants in Chinese criminal trials, the last chance for their voices to be heard prior to sentencing. Drawing upon the concept of voice and theories of speech acts and pragmatic equivalence, and based on the discourse analysis of seven authentic trial recordings, this study reveals how the discursive performance of the defendant is constructed, altered, and sometimes undermined through interpreting. The findings reveal that speech acts performed by the defendant are often not maintained in the interpreted renditions and that the concept of closing statements is difficult to convey. It is argued that when interpreters fail to convey the pragmatic force of defendants’ utterances, the voice of the defendants is not fully heard, which places them at a disadvantage and impacts upon their right to equality and justice. The article also reveals system-bound constraints on the effective provision of language assistance and the safeguarding of defendants’ legal rights.


Geophysics ◽  
2021 ◽  
pp. 1-74
Author(s):  
Elizabeth Maag-Capriotti ◽  
Yaoguo Li

Gravity gradiometry inversion can provide important knowledge about a salt body and assist in subsalt imaging. However, such inversions are faced with difficulties associated with the lack of response from the nil zone in which the salt density is nearly identical to that of the background sediments and weak signals from the deeper portion of the salt. It is well understood that such difficulties could be alleviated by incorporating prior information, such as the top of salt from seismic imaging and petrophysical data, into the inversions. How to effectively incorporate such prior information is still a challenge, and what level of increased knowledge such constrained inversions can provide remains to be understood. We have investigated and compared the additional knowledge provided by incorporating different forms of prior information, including a top-of-salt surface, and an expected density contrast model. These different types of information are incorporated through different strategies of constrained inversion, including an inversion with bound constraints on the density contrast, inversion after a reduction-to-binary process, and discrete-valued inversion. We apply these strategies first to synthetic gravity gradiometry data calculated from the SEG/EAGE salt body and evaluate the improvements to the recovered salt provided from successive imposition of increased prior information. We further apply the strategies to a set of marine gravity gradiometry data collected in the Gulf of Mexico and examine the additional knowledge gained from the imaging of the salt in the region. We show that much more valuable knowledge about the salt can be obtained with the right prior information imposed through an effective strategy, and demonstrate that such gravity gradiometry data contain information about the salt body at depths much greater than previously recognized.


2021 ◽  
Author(s):  
Jeremie Giraud ◽  
Vitaliy Ogarko ◽  
Roland Martin ◽  
Mark Jessell ◽  
Mark Lindsay

Abstract. The quantitative integration of geophysical measurements with data and information from other disciplines is becoming increasingly important in answering the challenges of undercover imaging and of the modelling of complex areas. We propose a review of the different techniques for the utilisation of structural, petrophysical and geological information in single physics and joint inversion as implemented in the Tomofast-x open-source inversion platform. We detail the range of constraints that can be applied to the inversion of potential field data. The inversion examples we show illustrate a selection of scenarios using a realistic synthetic dataset inspired by real-world geological measurements and petrophysical data from the Hamersley region (Western Australia). Using Tomofast-x’s flexibility, we investigate inversions combining the utilisation of petrophysical, structural and/or geological constraints while illustrating the utilisation of the L-curve principle to determine regularisation weights. Our results suggest that the utilisation of geological information to derive disjoint interval bound constraints is the most effective method to recover the true model. It is followed by model smoothness and smallness conditioned by geological uncertainty, and cross-gradient minimisation.


Sign in / Sign up

Export Citation Format

Share Document