3,355 research outputs found
Isostaticity and the solidification of semiflexible polymer melts
Using molecular dynamics simulations of a tangent-soft-sphere bead-spring
polymer model, we examine the degree to which semiflexible polymer melts
solidify at isostaticity. Flexible and stiff chains crystallize when they are
isostatic as defined by appropriate degree-of-freedom-counting arguments.
Semiflexible chains also solidify when isostatic if a generalized isostaticity
criterion that accounts for the slow freezing out of configurational freedom as
chain stiffness increases is employed. The dependence of the average
coordination number at solidification on chains' characteristic ratio
has the same functional form [] as the
dependence of the average coordination number at jamming on
in athermal systems, suggesting that jamming-related phenomena play
a significant role in thermal polymer solidification
Traditional Float Charges: are They Suited to Stationary Antimony-free Lead Acid Batteries?
International audienc
Multi-UAV trajectory planning problem using the difference of convex function programming
The trajectory planning problem for a swarm of multiple UAVs is known as a
challenging nonconvex optimization problem, particularly due to a large number
of collision avoidance constraints required for individual pairs of UAVs in the
swarm. In this paper, we tackle this nonconvexity by leveraging the difference
of convex function (DC) programming. We introduce the slack variables to relax
and reformulate the collision avoidance conditions and employ the penalty
function term to equivalently convert the problem into a DC form. Consequently,
we construct a penalty DC algorithm in which we sequentially solve a set of
convex optimization problems obtained by linearizing the collision avoidance
constraint. The algorithm iteratively tightens the safety condition and reduces
the objective cost of the planning problem and the additional penalty term.
Numerical results demonstrate the effectiveness of the proposed approach in
planning a large number of UAVs in congested space.Comment: This paper has been accepted for presentation at the 62nd IEEE
Conference on Decision and Control (CDC 2023
Childhood hospitalisation and related deaths in Hanoi, Vietnam: a tertiary hospital database analysis from 2007 to 2014
To describe hospital admission and emergency visit rates and potential risk factors of prolonged hospitalisation and death among children in Hanoi.; A retrospective study reviewed 212 216 hospitalisation records of children (aged 0-17) who attended the Vietnam National Children's Hospital in Hanoi between 2007 and 2014. Four indicators were analysed and reported: (1) rate of emergency hospital visits, (2) rate of hospitalisation, (3) length of hospital stay and (4) number of deaths. The risk of prolonged hospitalisation was investigated using Cox proportion hazard, and the risk of death was investigated through logistic regressions.; During 2007-2014, the average annual rate of emergency visits was 2.2 per 1000 children and the rate of hospital admissions was 13.8 per 1000 children. The annual rates for infants increased significantly by 3.9 per 1000 children during 2012-2014 for emergency visits and 25.1 per 1000 children during 2009-2014 for hospital admissions. Digestive diseases (32.0%) and injuries (30.2%) were common causes of emergency visits, whereas respiratory diseases (37.7%) and bacterial and parasitic infections (19.8%) accounted for most hospital admissions. Patients with mental and behavioural disorders remained in the hospital the longest (median=12 days). Morbidities related to the perinatal period dominated mortality causes (32.5% of deaths among those admitted to the hospital. Among the respiratory diseases, pneumonia was the leading cause of both prolonged hospitalisation and death.; Preventable health problems, such as common bacterial infections and respiratory diseases, were the primary causes of hospital admissions in Vietnam
Recovery from intrauterine Growth restriction in piglets defined by their headshape: a pilot study
Exercise-based cardiac rehabilitation in heart transplant recipients
This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:
To determine the effectiveness and safety of exercise‐based rehabilitation on the mortality, hospital admissions, morbidity, exercise capacity, health‐related quality of life, and return to work of people after heart transplantation
Scalable Focused Ion Beam Creation of Nearly Lifetime-Limited Single Quantum Emitters in Diamond Nanostructures
The controlled creation of defect center---nanocavity systems is one of the
outstanding challenges for efficiently interfacing spin quantum memories with
photons for photon-based entanglement operations in a quantum network. Here, we
demonstrate direct, maskless creation of atom-like single silicon-vacancy (SiV)
centers in diamond nanostructures via focused ion beam implantation with nm lateral precision and nm positioning accuracy relative to a
nanocavity. Moreover, we determine the Si+ ion to SiV center conversion yield
to and observe a 10-fold conversion yield increase by additional
electron irradiation. We extract inhomogeneously broadened ensemble emission
linewidths of GHz, and close to lifetime-limited single-emitter
transition linewidths down to MHz corresponding to -times
the natural linewidth. This demonstration of deterministic creation of
optically coherent solid-state single quantum systems is an important step
towards development of scalable quantum optical devices
imageseg: An R package for deep learning-based image segmentation
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
© 2022 The Authors. Methods in Ecology and Evolution published by John Wiley & Sons Ltd on behalf of British Ecological SocietyConvolutional neural networks (CNNs) and deep learning are powerful and robust tools for ecological applications and are particularly suited for image data. Image segmentation (the classification of all pixels in images) is one such application and can, for example, be used to assess forest structural metrics. While CNN-based image segmentation methods for such applications have been suggested, widespread adoption in ecological research has been slow, likely due to technical difficulties in implementation of CNNs and lack of toolboxes for ecologists. Here, we present R package imageseg which implements a CNN-based workflow for general purpose image segmentation using the U-Net and U-Net++ architectures in R. The workflow covers data (pre)processing, model training and predictions. We illustrate the utility of the package with image recognition models for two forest structural metrics: tree canopy density and understorey vegetation density. We trained the models using large and diverse training datasets from a variety of forest types and biomes, consisting of 2877 canopy images (both canopy cover and hemispherical canopy closure photographs) and 1285 understorey vegetation images. Overall segmentation accuracy of the models was high with a Dice score of 0.91 for the canopy model and 0.89 for the understorey vegetation model (assessed with 821 and 367 images respectively). The image segmentation models performed significantly better than commonly used thresholding methods and generalized well to data from study areas not included in training. This indicates robustness to variation in input images and good generalization strength across forest types and biomes. The package and its workflow allow simple yet powerful assessments of forest structural metrics using pretrained models. Furthermore, the package facilitates custom image segmentation with single or multiple classes and based on colour or grayscale images, for example, for applications in cell biology or for medical images. Our package is free, open source and available from CRAN. It will enable easier and faster implementation of deep learning-based image segmentation within R for ecological applications and beyond.publishedVersio
New Forests and New Forest People in Central Vietnam: The Acacia Boom
Vietnam is the country with the largest area of plantations of Australasian Acacia species (‘wattles’) in South-East Asia. Between 6 and 9% of the national land area is cultivated with tropical wattles (A. auriculiformis, A. mangium and A. × mangiiformis). From the perspective of its promoters, the wattle plantation industry in Vietnam may be seen as a success beyond expectations. We review the origins of this boom and ask what it has done to and for the coun- try’s landscape and people. The chapter combines findings and insights from an interdisciplinary research project in Thừa Thiên Huế province, north-central Vietnam. Research took place across upland and lowland wattle-growing regions, with ethnic minorities as well as the Kinh majority, and with long-term wattle growers as well as new en- trants. It drew on questionnaires, interviews and observations, as well as information from remote sensing, eco- logical surveys and hydrological assessments. We first describe how substantial areas of ‘new forest’ (short-rotation wattle plantations) were created, initially in degraded bushland, but now sometimes through clearing of highly bi- odiverse natural forest stands. These wattle plantations alter local hydrology, soils and biodiversity, and are exposed to risks including soil erosion and plant pathogens. The plantations provide wood chips and timber, supporting rev- enue, employment and a strong forestry industry. Incomes have risen appreciably for many, although unequally, and a class of successful entrepreneurs has emerged. These plantations alter the livelihoods and identities of upland ‘forest people’, historically shifting cultivators, contributing to what might be called ‘new forest people’. Ethnic mi- nority villagers are building new identities around the wattle economy and around their contracts with state forest agencies, seeing themselves increasingly as forest growers and protectors. We conclude by raising some questions regarding the social changes and issues of environmental sustainability linked to this wattle boom
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