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Aiming at the issues of traditional ant colony algorithm (ACO) in mobile robot path planning, including initial search blindness, susceptibility to local optima, and slow convergence, this paper proposes a multi-strategy improved ant colony algorithm (MS-ACO). Firstly, dynamic non-uniform distribution of initial pheromones is implemented by integrating the repulsive field from artificial the potential field method. Secondly, the heuristic information is enhanced to improve global search capability while constraining unnecessary path turns. Thirdly, an improved pheromone update strategy is developed by adopting distinct updating mechanisms for different evolutionary phases. Finally, dynamic parameter adaptation is achieved through optimized weight coefficients and volatility coefficients that coordinate with the pheromone update strategy, better aligning with the iterative characteristics of ant colony optimization. Experimental results demonstrate that MS-ACO effectively addresses the limitations of traditional ACO. Under identical experimental conditions, it achieves a 30.4% reduction in path length, 37.8% decrease in pathfinding time, and 71% fewer turns compared to conventional methods, verifying the feasibility and superiority of the proposed algorithm.
As an ambivalent symbol of America’s relationship with the natural world of wild things, the bear acquired new importance in the years of Theodore Roosevelt’s presidency (1901–1909). This article offers an interpretation of the significance of the bear at this time, looking at outdoor sportswriting and the cultural response to Roosevelt’s own bear-hunting exploits in that context. It finds two contrasting ideas of the bear, which appears both as a ferocious beast and as a bearskin trophy, a symbol of nature’s uncontrollable power and also a consumer object. Bear-hunting stories, it is proposed here, thus bridged two worlds: that of wild nature and that of human modernity. This, it suggests, was also the essential cultural function of Theodore Roosevelt’s public persona. Serving as president while assuming the unofficial role of bear-hunter-in-chief, and then becoming indelibly associated with sentimentalized cartoon or teddy bears, his image blurred the distinctions between the White House and the Rocky Mountains, modern life and the natural world. It is suggested in this way that the symbolism of the bear enabled Americans to navigate a way into the twentieth century, avoiding a hard choice between industrial modernity and wild nature by retaining a cultural space for both.
Mieko Shiomi (b. 1938) is a pioneering Japanese artist, composer, and performer, known for her lifelong practice that crosses the boundaries between music, visual art, and performance, which has evolved fluidly across cultures, media, and technologies. She co-founded a leading postwar Japanese experimental music collective, Group Ongaku, and later joined Fluxus at the invitation of George Maciunas, which led her to spend a year in New York from 1964–65. This article presents 11 images from an extended interview with Shiomi, conducted by composers Chikako Morishita and Akiko Yamane during their visit to her home in Osaka in January 2020, as part of the filming of the documentary Shadow Piece. In the interview, Shiomi reflects on her childhood, education, career, and family life, and discusses the creation and reception of works such as Endless Box, Mirror Piece, and Spatial Poem. The conversation, originally in Japanese, was translated into English by Kiyo Kamisawa and the author.
Interface-resolved direct numerical simulations are performed to investigate bubble-induced transition from a laminar to elasto-inertial turbulent (EIT) state in a pressure-driven viscoelastic square channel flow. The Giesekus model is used to account for the viscoelasticity of the continuous phase, while the dispersed phase is Newtonian. Simulations are performed for both single- and two-phase flows for a wide range of Reynolds (${Re}$) and Weissenberg (${\textit{Wi}}$) numbers. In the absence of any discrete external perturbations, single-phase viscoelastic flow is transitioned to an EIT regime at a critical Weissenberg number ($Wi_{cr})$ that decreases with increasing ${Re}$. It is demonstrated that injection of bubbles into a laminar viscoelastic flow introduces streamline curvature that is sufficient to trigger an elastic instability leading to a transition to an EIT regime. The temporal turbulent kinetic energy spectrum shows a scaling of $-2$ for this multiphase EIT regime, and this scaling is found to be independent of size and number of bubbles injected into the flow. It is also observed that bubbles move towards the channel centreline and form a string-shaped alignment pattern in the core region at the lower values of ${Re}=10$ and ${\textit{Wi}}=1$. In this regime, there are disturbances in the core region in the vicinity of bubbles while flow remains essentially laminar. Unlike the solid particles, it is found that increasing shear-thinning effect breaks up the alignment of bubbles.
This paper introduces the general ideas for parametric integral stochastic orders, with which a continuum of parametric functions are defined as a bridge between different classes of non-parametric functions. This approach allows one to identify a parametric function class over which two given random variables may violate the non-parametric stochastic order with specific patterns. The parameter used to name the parametric function class also measures the ratio of dominance violation for the corresponding non-parametric stochastic orders. Our framework, expanding the domain of stochastic orders, covers the existing studies of almost stochastic dominance. This leads to intuitive explanations and simpler proofs of existing results and their extensions.
Through a range of coping strategies, individuals seek to manage the stressors to which they are exposed, employing cognitive and behavioral responses that shape their emotional regulation of such events. Emergency first responders are routinely subjected to high-stress situations due to the nature of their duties and the continuous care of critically ill patients. This sustained exposure significantly increases their vulnerability to the development of mental health disorders, notably posttraumatic stress disorder (PTSD).
Objective:
The aim of this study was to determine the coping strategies used by first responders when facing critical incidents and their association with PTSD.
Methods:
A cross-sectional analytical study was conducted in 2022. All first responders from a volunteer fire department in a major Colombian city who voluntarily agreed to participate were included in the study. The participants were 28 ambulance crew members and 187 firefighters. Descriptive statistics were used for data analysis, and logistic regression models were applied to assess associations with PTSD. Principal components analysis was used to compute total scores, while the Lasso Method identified significant predictors.
Results:
The first responders most often employed avoidance and denial as coping strategies in response to the demands of their work in the prehospital field. After witnessing devastating events, many of them turned to religion for stress relief.
Conclusions:
The study identified the use of maladaptive strategies associated with PTSD among staff, making it critical to develop training programs that help first responders cope with critical incidents by developing adaptive coping skills.