To save content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about saving content to .
To save content items to your Kindle, first ensure no-reply@cambridge.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
To address the issues of low positioning accuracy and weak robustness of prior visual simultaneous localization and mapping (VSLAM) systems in dynamic environments, a semantic VSLAM (Sem-VSLAM) approach based on deep learning is proposed in this article. The proposed Sem-VSLAM algorithm adds semantic segmentation threads in parallel based on the open-source ORB-SLAM2’s visual odometry. First, while extracting the ORB features from an RGB-D image, the frame image is semantically segmented, and the segmented results are detected and repaired. Then, the feature points of dynamic objects are eliminated by using semantic information and motion consistency detection, and the poses are estimated by using the remaining feature points after the dynamic feature elimination. Finally, a 3D point cloud map is constructed by using tracking information and semantic information. The experiment uses Technical University of Munich public data to show the usefulness of the Sem-VSLAM algorithm. The experimental results show that the Sem-VSLAM algorithm can reduce the absolute trajectory error and relative attitude error of attitude estimation by about 95% compared to the ORB-SLAM2 algorithm and by about 14% compared to the VO-YOLOv5s in a highly dynamic environment and the average time consumption of tracking each frame image reaches 61 ms. It is verified that the Sem-VSLAM algorithm effectively improves the robustness and positioning accuracy in high dynamic environment and owning a satisfying real-time performance. Therefore, the Sem-VSLAM has a better mapping effect in a highly dynamic environment.
where $d \geq 1$, $\mu \in \mathbb{R}$ and $0 \lt \sigma \lt \infty$ if $1 \leq d \leq 4$ and $0 \lt \sigma \lt 4/(d-4)$ if $d \geq 5$. In the mass critical and supercritical cases, we establish the existence of blowup solutions to the problem for cylindrically symmetric data. The result extends the known ones with respect to blowup of solutions to the problem for radially symmetric data.
Age-related changes can affect mental health, but aging-focused mental health research is limited. The objective was to identify the top 10 unanswered research questions on aging and mental health according to what matters most to aging Canadians. A steering group of experts-by-experience (e.g., older adults, caregivers, health and social care providers) guided three phases of a modified James Lind Alliance priority-setting partnership: (1) a broad national survey (n = 305) and a rapid literature scan; (2) a follow-up national survey (n = 703); and (3) four online workshops (n = 52) with a nominal group technique. Forty-two unique questions on aging and mental health resulted, of which 18 were determined to be answered by existing evidence. Of the 25 partially and unanswered questions, 10 were ranked as top priority. Findings can be used to prioritize future research, knowledge mobilization, and funding decisions, and to promote and support collaboration between longstanding siloed research and care fields.
As most mathematically justifiable Lagrangian coherent structure detection methods rely on spatial derivatives, their applicability to sparse trajectory data has been limited. For experimental fluid dynamicists and natural scientists working with Lagrangian trajectory data via passive tracers in unsteady flows (e.g. Lagrangian particle tracking or ocean buoys), obtaining material measures of fluid rotation or stretching is an active topic of research. To facilitate frame-indifferent investigations in unsteady and sparsely sampled flows, we present a novel approach to quantify fluid stretching and rotation via relative Lagrangian velocities. This technique provides a formal objective extension of quasi-objective metrics to unsteady flows by accounting for mean flow behaviour. For extremely sparse experimental data, fluid structures may be significantly undersampled and the mean flow behaviour becomes difficult to quantify. We provide a means to maintain the accuracy of our novel sparse flow diagnostics in extremely sparse sampling scenarios, such as ocean buoy data and Lagrangian particle tracking. We use data from multiple numerical and experimental flows to show that our methods can identify structures beyond existing limits of sparse, frame-indifferent diagnostics and exhibit improved interpretability over common frame-dependent diagnostics.
This research investigates the wake–foil interactions between two oscillating foils in a tandem configuration undergoing energy harvesting kinematics. Oscillating foils have been shown to extract hydrokinetic energy from free-stream flows through a combination of periodic heave and pitch motions, at relatively higher amplitudes and lower reduced frequency than thrust generating foils. When placed in tandem, the wake–foil interactions can govern the energy harvesting efficiency of the system due to a reduced relative flow velocity in combination with a structured and coherent wake of vortices shed from the high amplitude flapping of upstream foils. This work utilizes simulations of two tandem foils to parameterize and model the energy harvesting performance as a function of array configuration and foil kinematics. Once the wake of the leading foil has been fully parameterized, the placement, phase angle and kinematic stroke of the second foil is utilized to estimate the time-dependent power curve. The algorithm predicts the power of the second foil through the mean and unsteady wake characteristics, including the direct impingement of a vortex with the trailing foil.
Iguaçu National Park, a UNESCO World Heritage Site, faces threats from proposed legislation aimed at downgrading its protection to allow reopening of the Caminho-do-Colono road, which would fragment the National Park. This study assesses the National Park’s importance in preserving native vegetation and its economic significance via payments for environmental services. We evaluated different scenarios, demonstrating how these resources are vital for certain municipalities. By comparing economic performance before and after the road’s closure, our findings reveal that, contrary to local beliefs, the closure did not negatively impact the local economy. Additionally, these legislative bills are legally infeasible and fail to offer environmental or economic benefits, favouring small interest groups over the collective good. This research highlights that the Caminho-do-Colono road is not a viable approach to municipal development. Instead, maintaining the National Park’s integrity is crucial for both ecological preservation and economic stability in the region. Our analysis underscores the broader implications of environmental conservation efforts and the necessity of rejecting projects that compromise protected areas. This study provides a comprehensive evaluation of the National Park’s role, emphasizing the need for sustainable development that aligns with environmental and community well-being.
A numerical method is proposed for a class of one-dimensional stochastic control problems with unbounded state space. This method solves an infinite-dimensional linear program, equivalent to the original formulation based on a stochastic differential equation, using a finite element approximation. The discretization scheme itself and the necessary assumptions are discussed, and a convergence argument for the method is presented. Its performance is illustrated by examples featuring long-term average and infinite horizon discounted costs, and additional optimization constraints.
Language is one of the most celebrated hallmarks of human cognition. With the continuous improvement of medical technology, functional MRI (fMRI) has been used in aphasia. Although many related studies have been carried out, most studies have not extensively focused on brain regions with reduced activation in aphasic patients. The aim of this study was to identify brain regions normally activated in healthy controls but with reduced activation in aphasic patients during fMRI language tasks.
Methods:
We collected all previous task-state fMRI studies of secondary aphasia. The brain regions showed normal activation in healthy controls and reduced activation in aphasic patients were conducted activation likelihood estimation (ALE) meta-analysis to obtain the brain regions with consistently reduced activation in aphasic patients.
Results:
The ALE meta-analysis revealed that the left inferior frontal gyrus, left middle temporal gyrus, left superior temporal gyrus, left fusiform gyrus, left lentiform nucleus and the culmen of the cerebellum were the brain regions with reduced activation in aphasic patients.
Discussion:
These findings from the ALE meta-analysis have significant implications for understanding the language network and the potential for recovery of language functions in individuals with aphasia.
The Qing dynasty enforced a policy of separate governance for the people of the Eight Banners, ruling that bannermen were neither to be administered under the regular civilian administrative system, nor listed on the civilian register. Institutionally and legally, the labels “Banner” (qi 旗) and “civilian” (min 民) marked a fundamental divide between different social groups in the Qing. However, in actual practice, the boundary between the two was less rigid. An ambiguous area existed within the seemingly strict legal and administrative regime, providing opportunists with an abundance of loopholes to exploit. Some changed their status from “civilian commoner” to “bannermen” to acquire land, while others moved from “bannermen” status to “civilian commoner” status to pursue promotion in the civil service. Shedding light on the everyday lives of these people, this article delves into the intricate Banner–civilian classification of the Qing dynasty, with a focus on the overlapping area between the parallel systems. It aims to rectify the conventional binary perspective that strictly dichotomizes Banner and civilian status. By doing so, it highlights the multifaceted nature and diversity inherent in Qing ethnic relations and local society.
The spatial evolution of various statistical parameters of fetch-limited waves generated by steadily blowing wind over mean water flow in a wind-wave flume is investigated experimentally. Measurements are performed in both along- and against-wind current conditions, and compared with measurements in the absence of current. A rake of capacitance-type wave gauges is used to measure surface elevation for a wide range of wind and water current velocities; additionally, an optical wave gauge is used to measure the directional properties of the wind-wave field in the presence of a mean water current at multiple locations. The variation with fetch of essential wave parameters such as characteristic wave energy, dominant frequency, power spectra and temporal coherence, as well as higher-order statistical moments that characterize wave shape, is presented for co- and counter-wind water currents, and compared with the no-current condition. The findings in the presence of mean water flow are interpreted in the framework of the viscous shear flow instability model of Geva & Shemer (Phys. Rev. Lett., vol. 128, 2022, 124501).
We investigate some aspects of the problem of the estimation of birth distributions (BDs) in multi-type Galton–Watson trees (MGWs) with unobserved types. More precisely, we consider two-type MGWs called spinal-structured trees. This kind of tree is characterized by a spine of special individuals whose BD $\nu$ is different from the other individuals in the tree (called normal, and whose BD is denoted by $\mu$). In this work, we show that even in such a very structured two-type population, our ability to distinguish the two types and estimate $\mu$ and $\nu$ is constrained by a trade-off between the growth-rate of the population and the similarity of $\mu$ and $\nu$. Indeed, if the growth-rate is too large, large deviation events are likely to be observed in the sampling of the normal individuals, preventing us from distinguishing them from special ones. Roughly speaking, our approach succeeds if $r\lt \mathfrak{D}(\mu,\nu)$, where r is the exponential growth-rate of the population and $\mathfrak{D}$ is a divergence measuring the dissimilarity between $\mu$ and $\nu$.
The present study reports experiments of water droplets impacting on ice or on a cold metal substrate, with the aim of understanding the effects of liquid solidification or substrate melting on the impingement process. Both liquid and substrate temperatures are varied, as well as the height of fall of the droplet. The dimensionless maximum spreading diameter, $\beta _m$, is found to increase with both temperatures as well as with the impact velocity. Here $\beta _m$ is reduced when liquid solidification, which enhances dissipation, is present, whereas fusion, i.e. substrate melting, favours the spreading of the impacting droplet. These observations are rationalized by extending an existing model of effective viscosity, in which phase change alters the size and shape of the developing viscous boundary layer, thereby modifying the value of $\beta _m$. The use of this correction allows us to adapt a scaling recently developed in the context of isothermal drop impacts to propose a law giving the maximum diameter of an impacting water droplet in the presence of melting or solidification. Finally, additional experiments of dimethyl sulfoxide drop impacts onto a cold brass substrate have been performed and are also captured by the proposed modelling, generalizing our results to other fluids.
Globally, companies are developing and implementing their strategies to reduce greenhouse gas emissions to limit the global temperature increase to 1.5 degrees Celsius above pre-industrial levels, in line with the Paris Agreement. However, there is also growing recognition and awareness of the potential negative impacts of these activities on human rights. Recent pressure from international normative standards and ESG expectations, emerging legislative developments, and legal precedents are driving companies to consider human rights impacts across their climate action. This piece explores some of the human rights risks associated with the transition to renewable energy; the transformation to regenerative agriculture; the scaling up of the circular economy; and the implementation of nature-based solutions. It then explores the challenges of conducting effective human rights due diligence given the scale and scope of the transitions needed and provides examples of how companies are seeking to respect human rights in their climate action.