82 research outputs found
The Weakest Failure Detector for Solving Wait-Free, Eventually Bounded-Fair Dining Philosophers
This dissertation explores the necessary and sufficient conditions to solve a variant
of the dining philosophers problem. This dining variant is defined by three properties:
wait-freedom, eventual weak exclusion, and eventual bounded fairness. Wait-freedom
guarantees that every correct hungry process eventually enters its critical
section, regardless of process crashes. Eventual weak exclusion guarantees that every
execution has an infinite suffix during which no two live neighbors execute overlapping
critical sections. Eventual bounded fairness guarantees that there exists a
fairness bound k such that every execution has an infinite suffix during which no
correct hungry process is overtaken more than k times by any neighbor. This dining
variant (WF-EBF dining for short) is important for synchronization tasks where eventual
safety (i.e., eventual weak exclusion) is sufficient for correctness (e.g., duty-cycle
scheduling, self-stabilizing daemons, and contention managers).
Unfortunately, it is known that wait-free dining is unsolvable in asynchronous
message-passing systems subject to crash faults. To circumvent this impossibility
result, it is necessary to assume the existence of bounds on timing properties, such
as relative process speeds and message delivery time. As such, it is of interest to
characterize the necessary and sufficient timing assumptions to solve WF-EBF dining.
We focus on implicit timing assumptions, which can be encapsulated by failure detectors. Failure detectors can be viewed as distributed oracles that can be queried
for potentially unreliable information about crash faults. The weakest detector D for
WF-EBF dining means that D is both necessary and sufficient. Necessity means that
every failure detector that solves WF-EBF dining is at least as strong as D. Sufficiency
means that there exists at least one algorithm that solves WF-EBF dining using D.
As such, our research goal is to characterize the weakest failure detector to solve
WF-EBF dining.
We prove that the eventually perfect failure detector 3P is the weakest failure
detector for solving WF-EBF dining. 3P eventually suspects crashed processes permanently,
but may make mistakes by wrongfully suspecting correct processes finitely
many times during any execution. As such, 3P eventually stops suspecting correct
processes
Progressive multi-atlas label fusion by dictionary evolution
AbstractAccurate segmentation of anatomical structures in medical images is important in recent imaging based studies. In the past years, multi-atlas patch-based label fusion methods have achieved a great success in medical image segmentation. In these methods, the appearance of each input image patch is first represented by an atlas patch dictionary (in the image domain), and then the latent label of the input image patch is predicted by applying the estimated representation coefficients to the corresponding anatomical labels of the atlas patches in the atlas label dictionary (in the label domain). However, due to the generally large gap between the patch appearance in the image domain and the patch structure in the label domain, the estimated (patch) representation coefficients from the image domain may not be optimal for the final label fusion, thus reducing the labeling accuracy. To address this issue, we propose a novel label fusion framework to seek for the suitable label fusion weights by progressively constructing a dynamic dictionary in a layer-by-layer manner, where the intermediate dictionaries act as a sequence of guidance to steer the transition of (patch) representation coefficients from the image domain to the label domain. Our proposed multi-layer label fusion framework is flexible enough to be applied to the existing labeling methods for improving their label fusion performance, i.e., by extending their single-layer static dictionary to the multi-layer dynamic dictionary. The experimental results show that our proposed progressive label fusion method achieves more accurate hippocampal segmentation results for the ADNI dataset, compared to the counterpart methods using only the single-layer static dictionary
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Roadmap on commercialization of metal halide perovskite photovoltaics
Perovskite solar cells (PSCs) represent one of the most promising emerging photovoltaic technologies due to their high power conversion efficiency. However, despite the huge progress made not only in terms of the efficiency achieved, but also fundamental understanding of the relevant physics of the devices and issues which affect their efficiency and stability, there are still unresolved problems and obstacles on the path toward commercialization of this promising technology. In this roadmap, we aim to provide a concise and up to date summary of outstanding issues and challenges, and the progress made toward addressing these issues. While the format of this article is not meant to be a comprehensive review of the topic, it provides a collection of the viewpoints of the experts in the field, which covers a broad range of topics related to PSC commercialization, including those relevant for manufacturing (scaling up, different types of devices), operation and stability (various factors), and environmental issues (in particular the use of lead). We hope that the article will provide a useful resource for researchers in the field and that it will facilitate discussions and move forward toward addressing the outstanding challenges in this fast-developing field
Evaluation of Efficacy and Safety of Dan’e-Fukang Soft Extract in the Treatment of Endometriosis: A Meta-Analysis of 39 Randomized Controlled Trials Enrolling 5442 Patients
Objective. To systematically evaluate the efficacy and safety of Dan’e-fukang soft extract in endometriosis treatment. Method. PubMed, CNKI, Wanfang Database, VIP, SinoMed, and Cochrane Library were searched. Randomized controlled trials (RCTs) comparing the efficacy of Dan’e-fukang soft extract and conventional western medicines for endometriosis treatment were included. The data were extracted independently by two people and analyzed using RevMan 5.2.0 software. The relative risk (RR) and mean difference (MD) with 95% confidence intervals were considered as effective outcome indicators. Results. Thirty-nine papers including 5442 patients with endometriosis were included in this study. A meta-analysis revealed that Dan’e-fukang soft extract was more efficient than gestrinone in the treatment of endometriosis (RR = 1.08, 95% CI = 1.03 to 1.15, I2 = 71%, REM, 18 trials) and its efficacy was comparable to that of danazol and mifepristone. Dan’e-fukang soft extract was also as effective as gestrinone and mifepristone in terms of relapse rate and relieving dysmenorrhea. The incidence of adverse reactions was lower than that of conventional western medicines. Conclusions. The results of this study showed that Dan’e-fukang soft extract offers certain advantages in endometriosis treatment, but rigorously designed, strictly implemented RCTs are needed to further validate its efficacy
Dataset on the mechanical property of graphite after molten FLiNaK salt infiltration
Presented in this article are mechanical property and microstructural data for fluoride molten salt infiltrated graphite at high temperature. Four infiltration pressures (0 kPa, 450 kPa, 600 kPa, and 1000 kPa) and two kinds of graphite (IG-110 and NG-CT-10) were used during molten salt infiltration. After fluoride molten salt infiltration, compression testing and tension testing were performed at 700 °C to determine compressive strength, tensile strength, softening coefficient, stress–strain curve, and absorbed energy. Utilizing scanning electron microscopy (SEM) applied to fracture fragments, SEM micrographs for the fracture surface of molten salt infiltrated graphite and virgin graphite were determined. Keywords: Graphite, Fluoride molten salt, Infiltration, Mechanical strengt
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