space compression
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2022 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xiang Li ◽  
Yang Ming ◽  
Hongguang Ma ◽  
Kaitao (Stella) Yu

PurposeTravel time at inter-stops is a set of important parameters in bus timetabling, which is usually assumed to be normal (log-normal) random variable in literature. With the development of digital technology and big data analytics ability in the bus industry, practitioners prefer to generate deterministic travel time based on the on-board GPS data under maximum probability rule and mean value rule, which simplifies the optimization procedure, but performs poorly in the timetabling practice due to the loss of uncertain nature on travel time. The purpose of this study is to propose a GPS-data-driven bus timetabling approach with consideration of the spatial-temporal characteristic of travel time.Design/methodology/approachThe authors illustrate that the real-life on-board GPS data does not support the hypothesis of normal (log-normal) distribution on travel time at inter-stops, thereby formulating the travel time as a scenario-based spatial-temporal matrix, where K-means clustering approach is utilized to identify the scenarios of spatial-temporal travel time from daily observation data. A scenario-based robust timetabling model is finally proposed to maximize the expected profit of the bus carrier. The authors introduce a set of binary variables to transform the robust model into an integer linear programming model, and speed up the solving process by solution space compression, such that the optimal timetable can be well solved by CPLEX.FindingsCase studies based on the Beijing bus line 628 are given to demonstrate the efficiency of the proposed methodology. The results illustrate that: (1) the scenario-based robust model could increase the expected profits by 15.8% compared with the maximum probability model; (2) the scenario-based robust model could increase the expected profit by 30.74% compared with the mean value model; (3) the solution space compression approach could effectively shorten the computing time by 97%.Originality/valueThis study proposes a scenario-based robust bus timetabling approach driven by GPS data, which significantly improves the practicality and optimality of timetable, and proves the importance of big data analytics in improving public transport operations management.


Author(s):  
Martínez Rodas O ◽  

Fibrothecomas are benign ovarian stromal tumors, they are rare tumors of gonadal stromal cell origin that represent 3-4% of all ovarian tumors. It commonly occurs in post-menopausal women. The clinical presentation is often nonspecific, whereas patients more frequently present with a pelvic mass, metrorrhagia, and pelvic pain. We present a 35-year-old patient, nulli-pregnant, with no personal or family pathological history, who attended a medical consultation for presenting progressive abdominal distention of 6 months of evolution in addition to abdominal pain in the last 2 months type colic which increased during her menstrual periods concomitantly alteration in your defecatory habits. Abdominal ultrasound was performed, finding a solid intrapelvic mass of approximately 14x10x10 cm in diameter of probable left ovarian origin, free fluid in the Douglas space, compression and displacement of intestinal loops and bladder. The patient underwent surgery and an exploratory laparotomy was performed, finding a pelvic tumor adhered to the tube and left ovary, in addition to ascites fluid in the abdominal cavity, complete resection of the tumor, ovary and left salpingue was performed.


2021 ◽  
Vol 38 (6) ◽  
pp. 1801-1807
Author(s):  
Songjiao Wu

Standard actions are crucial to sports training of athletes and daily exercise of ordinary people. There are two key issues in sports action recognition: the extraction of sports action features, and the classification of sports actions. The existing action recognition algorithms cannot work effectively on sports competitions, which feature high complexity, fine class granularity, and fast action speed. To solve the problem, this paper develops an image recognition method of standard actions in sports videos, which merges local and global features. Firstly, the authors combed through the functions and performance required for the recognition of standard actions of sports, and proposed an attention-based local feature extraction algorithm for the frames of sports match videos. Next, a sampling algorithm was developed based on time-space compression, and a standard sports action recognition algorithm was designed based on time-space feature fusion, with the aim to fuse the time-space features of the standard actions in sports match videos, and to overcome the underfitting problem of direct fusion of time-space features extracted by the attention mechanism. The workflow of these algorithms was explained in details. Experimental results confirm the effectiveness of our approach.


Author(s):  
Haosen Liu ◽  
Fangqing Gu ◽  
Yiu-Ming Cheung

Numerous surrogate-assisted expensive multi-objective optimization algorithms were proposed to deal with expensive multi-objective optimization problems in the past few years. The accuracy of the surrogate models degrades as the number of decision variables increases. In this paper, we propose a surrogate-assisted expensive multi-objective optimization algorithm based on decision space compression. Several surrogate models are built in the lower dimensional compressed space. The promising points are generated and selected in the lower compressed decision space and decoded to the original decision space for evaluation. Experimental studies show that the proposed algorithm achieves a good performance in handling expensive multi-objective optimization problems with high-dimensional decision space.


Author(s):  
Jonathan A. Ward

We derive explicit formulae to quantify the Markov chain state-space compression, or lumping, that can be achieved in a broad range of dynamical processes on real-world networks, including models of epidemics and voting behaviour, by exploiting redundancies due to symmetries. These formulae are applied in a large-scale study of such symmetry-induced lumping in real-world networks, from which we identify specific networks for which lumping enables exact analysis that could not have been done on the full state-space. For most networks, lumping gives a state-space compression ratio of up to 10 7 , but the largest compression ratio identified is nearly 10 12 . Many of the highest compression ratios occur in animal social networks. We also present examples of types of symmetry found in real-world networks that have not been previously reported.


2021 ◽  
Vol 31 (4) ◽  
pp. 1-29
Author(s):  
Omar Hesham ◽  
Gabriel Wainer

Crowd simulation demands careful consideration in regard to the classic trade-off between accuracy and efficiency. Particle-based methods have seen success in various applications in architecture, military, urban planning, and entertainment. This method focuses on local dynamics of individuals in large crowds, with a focus on serious games and entertainment. The technique uses an area-based penalty force that captures the infringement of each entity's personal space. This method does not need a costly nearest-neighbor search and allows for an inherently data-parallel implementation capable of simulating thousands of entities at interactive frame rates. The algorithm reproduces personal space compression around motion barriers for moving crowds and around points of interest for static crowds.


2021 ◽  
pp. 1-19
Author(s):  
Jean-Michel Johnston

The Introduction presents the historiographical context and main themes of the book. It situates the book within discussions surrounding the process of scientific innovation and industrialization during the Sattelzeit, the process of ‘time-space’ compression associated with the communications revolution, the role of networks of transport and communication in the creation of regional and national identities, and the emergence of a new, connected middle class during the nineteenth century. Bringing together these narratives, the Introduction introduces the book’s principal argument—that, once shorn of its normative connotations, modernization remains a useful concept to illuminate the process through which state and society were transformed during the nineteenth century, and that networks played a crucial role in producing the profoundly ambivalent experience of modernity most often associated with the turn of the twentieth century. It ends with a description of the structure of the book as a whole.


2020 ◽  
Vol 11 (3) ◽  
pp. 122-145
Author(s):  
Tyler McCreary ◽  

This article examines the conflicting subjectivities and space-times of Indigenous and colonial law that underpin the recent shutdown of the Canadian economy as people barricaded railways and ports in solidarity with the Witsuwit'en hereditary chiefs’ blockade against the Coastal GasLink pipeline across their territory. The article argues that this conflict between Canadian and Witsuwit'en law reflects fundamental tensions between their respective foundations in relations of the commodity and the gift. Within settler capitalist society, the value of a commodity is constructed relationally through a political economy of exchange that aims to speed transactions to maximize profits. With an ongoing drive for time-space compression, there is continual pressure in settler capitalism to develop new infrastructure that can speed the circulation of commodities. In Witsuwit'en society, the gift presents a contrasting logic of place-time extension. Rather than focusing on closing transactions to increase profits, gift giving stretches reciprocal obligations into the past and future. Contrasting these distinct conceptions of the relationship between value and time, the article argues that the Witsuwit'en struggle with Coastal GasLink should be understood as conflict between colonial temporal enclosures and a radical promise to open futures different to those engendered by the colonial present.


2020 ◽  
Vol 27 (3) ◽  
pp. 87-92
Author(s):  
Rebecca Irons

Global lockdowns have resulted in a challenge to our carefully constructed notions of time, the work week and time-space compression. For the past few months, we have been living in ‘Quarantime’. Quarantime moves differently than our daily lived temporalities of routine and order, and forces us to question the intimate relationship that we may have with how we structure our daily lives around a clock and timesheet. This article questions the challenges and opportunities inherent within the disruption of routine intimacies enacted through Quarantime, drawing on case studies of clock time and the work week, and through examining Quarantime’s unique relationship to time-space compression. It will suggest that Quarantime opens up a space for us to question intimate attachments to enforced routine and wide institutionalised concepts of clock time.


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