196 research outputs found
An Actor-Critic-Based UAV-BSs Deployment Method for Dynamic Environments
In this paper, the real-time deployment of unmanned aerial vehicles (UAVs) as
flying base stations (BSs) for optimizing the throughput of mobile users is
investigated for UAV networks. This problem is formulated as a time-varying
mixed-integer non-convex programming (MINP) problem, which is challenging to
find an optimal solution in a short time with conventional optimization
techniques. Hence, we propose an actor-critic-based (AC-based) deep
reinforcement learning (DRL) method to find near-optimal UAV positions at every
moment. In the proposed method, the process searching for the solution
iteratively at a particular moment is modeled as a Markov decision process
(MDP). To handle infinite state and action spaces and improve the robustness of
the decision process, two powerful neural networks (NNs) are configured to
evaluate the UAV position adjustments and make decisions, respectively.
Compared with the heuristic algorithm, sequential least-squares programming and
fixed UAVs methods, simulation results have shown that the proposed method
outperforms these three benchmarks in terms of the throughput at every moment
in UAV networks
Controlling Class Layout for Deep Ordinal Classification via Constrained Proxies Learning
For deep ordinal classification, learning a well-structured feature space
specific to ordinal classification is helpful to properly capture the ordinal
nature among classes. Intuitively, when Euclidean distance metric is used, an
ideal ordinal layout in feature space would be that the sample clusters are
arranged in class order along a straight line in space. However, enforcing
samples to conform to a specific layout in the feature space is a challenging
problem. To address this problem, in this paper, we propose a novel Constrained
Proxies Learning (CPL) method, which can learn a proxy for each ordinal class
and then adjusts the global layout of classes by constraining these proxies.
Specifically, we propose two kinds of strategies: hard layout constraint and
soft layout constraint. The hard layout constraint is realized by directly
controlling the generation of proxies to force them to be placed in a strict
linear layout or semicircular layout (i.e., two instantiations of strict
ordinal layout). The soft layout constraint is realized by constraining that
the proxy layout should always produce unimodal proxy-to-proxies similarity
distribution for each proxy (i.e., to be a relaxed ordinal layout). Experiments
show that the proposed CPL method outperforms previous deep ordinal
classification methods under the same setting of feature extractor.Comment: Accepted by AAAI 202
Recent Advances in Organic Light-Emitting Diodes Based on Pure Organic Room Temperature Phosphorescence Materials
Pure organic room temperature phosphorescence (RTP) materials have attracted extensive attention in recent years due to their unique characteristics, such as flexible design method, low toxicity, low cost, as well as the ease of production at scale. The involvement of triplet state and direct radiative transition from the triplet state show that RTP materials have great potential as a new generation emitter in organic light-emitting diodes (OLEDs). Based on the mechanism of phosphorescence, various methods have been developed to achieve RTP emissions in the crystal state. However, the observation of RTP in the thin film state is much more difficult to achieve because of the lower degree of rigidity and suppression of the non-radiative transition. In this mini-review, molecular design strategies developed to achieve RTP emissions and their application in OLEDs are summarized and discussed. The conclusion and outlook point to great potential as well as the challenges for the continued study of pure organic RTP materials-based OLEDs
LawBench: Benchmarking Legal Knowledge of Large Language Models
Large language models (LLMs) have demonstrated strong capabilities in various
aspects. However, when applying them to the highly specialized, safe-critical
legal domain, it is unclear how much legal knowledge they possess and whether
they can reliably perform legal-related tasks. To address this gap, we propose
a comprehensive evaluation benchmark LawBench. LawBench has been meticulously
crafted to have precise assessment of the LLMs' legal capabilities from three
cognitive levels: (1) Legal knowledge memorization: whether LLMs can memorize
needed legal concepts, articles and facts; (2) Legal knowledge understanding:
whether LLMs can comprehend entities, events and relationships within legal
text; (3) Legal knowledge applying: whether LLMs can properly utilize their
legal knowledge and make necessary reasoning steps to solve realistic legal
tasks. LawBench contains 20 diverse tasks covering 5 task types: single-label
classification (SLC), multi-label classification (MLC), regression, extraction
and generation. We perform extensive evaluations of 51 LLMs on LawBench,
including 20 multilingual LLMs, 22 Chinese-oriented LLMs and 9 legal specific
LLMs. The results show that GPT-4 remains the best-performing LLM in the legal
domain, surpassing the others by a significant margin. While fine-tuning LLMs
on legal specific text brings certain improvements, we are still a long way
from obtaining usable and reliable LLMs in legal tasks. All data, model
predictions and evaluation code are released in
https://github.com/open-compass/LawBench/. We hope this benchmark provides
in-depth understanding of the LLMs' domain-specified capabilities and speed up
the development of LLMs in the legal domain
Extinction risk of Chinese angiosperms varies between woody and herbaceous species
Aim: Understanding how species' traits and environmental contexts relate to extinction risk is a critical priority for ecology and conservation biology. This study aims to identify and explore factors related to extinction risk between herbaceous and woody angiosperms to facilitate more effective conservation and management strategies and understand the interactions between environmental threats and species' traits. Location: China. Taxon: Angiosperms. Methods: We obtained a large dataset including five traits, six extrinsic variables, and 796,118 occurrence records for 14,888 Chinese angiosperms. We assessed the phylogenetic signal and used phylogenetic generalized least squares regressions to explore relationships between extinction risk, plant traits, and extrinsic variables in woody and herbaceous angiosperms. We also used phylogenetic path analysis to evaluate causal relationships among traits, climate variables, and extinction risk of different growth forms. Results: The phylogenetic signal of extinction risk differed among woody and herbaceous species. Angiosperm extinction risk was mainly affected by growth form, altitude, mean annual temperature, normalized difference vegetation index, and precipitation change from 1901 to 2020. Woody species' extinction risk was strongly affected by height and precipitation, whereas extinction risk for herbaceous species was mainly affected by mean annual temperature rather than plant traits. Main conclusions: Woody species were more likely to have higher extinction risks than herbaceous species under climate change and extinction threat levels varied with both plant traits and extrinsic variables. The relationships we uncovered may help identify and protect threatened plant species and the ecosystems that rely on them
The provenance of Taklamakan desert sand
Sand migration in the vast Taklamakan desert within the Tarim Basin (Xinjiang Uyghur Autonomous region, PR China) is governed by two competing transport agents: wind and water, which work in diametrically opposed directions. Net aeolian transport is from northeast to south, while fluvial transport occurs from the south to the north and then west to east at the northern rim, due to a gradual northward slope of the underlying topography. We here present the first comprehensive provenance study of Taklamakan desert sand with the aim to characterise the interplay of these two transport mechanisms and their roles in the formation of the sand sea, and to consider the potential of the Tarim Basin as a contributing source to the Chinese Loess Plateau (CLP). Our dataset comprises 39 aeolian and fluvial samples, which were characterised by detrital-zircon U–Pb geochronology, heavy-mineral, and bulk-petrography analyses. Although the inter-sample differences of all three datasets are subtle, a multivariate statistical analysis using multidimensional scaling (MDS) clearly shows that Tarim desert sand is most similar in composition to rivers draining the Kunlun Shan (south) and the Pamirs (west), and is distinctly different from sediment sources in the Tian Shan (north). A small set of samples from the Junggar Basin (north of the Tian Shan) yields different detrital compositions and age spectra than anywhere in the Tarim Basin, indicating that aeolian sediment exchange between the two basins is minimal. Although river transport dominates delivery of sand into the Tarim Basin, wind remobilises and reworks the sediment in the central sand sea. Characteristic signatures of main rivers can be traced from entrance into the basin to the terminus of the Tarim River, and those crossing the desert from the south to north can seasonally bypass sediment through the sand sea. Smaller ephemeral rivers from the Kunlun Shan end in the desert and discharge their sediment there. Both river run-off and wind intensity are strongly seasonal, their respective transport strength and opposing directions maintain the Taklamakan in its position and topography
Efficacy and safety of tigecycline monotherapy vs. imipenem/cilastatin in Chinese patients with complicated intra-abdominal infections: a randomized controlled trial
<p>Abstract</p> <p>Background</p> <p>Tigecycline, a first-in-class broad-spectrum glycylcycline antibiotic, has broad-spectrum in vitro activity against bacteria commonly encountered in complicated intra-abdominal infections (cIAIs), including aerobic and facultative Gram-positive and Gram-negative bacteria and anaerobic bacteria. In the current trial, tigecycline was evaluated for safety and efficacy vs. imipenem/cilastatin in hospitalized Chinese patients with cIAIs.</p> <p>Methods</p> <p>In this phase 3, multicenter, open-label study, patients were randomly assigned to receive IV tigecycline or imipenem/cilastatin for ≤2 weeks. The primary efficacy endpoints were clinical response at the test-of-cure visit (12-37 days after therapy) for the microbiologic modified intent-to-treat and microbiologically evaluable populations. Because the study was not powered to demonstrate non-inferiority between tigecycline and imipenem/cilastatin, no formal statistical analysis was performed. Two-sided 95% confidence intervals (CIs) were calculated for the response rates in each treatment group and for differences between treatment groups for descriptive purposes.</p> <p>Results</p> <p>One hundred ninety-nine patients received ≥1 dose of study drug and comprised the modified intent-to-treat population. In the microbiologically evaluable population, 86.5% (45 of 52) of tigecycline- and 97.9% (47 of 48) of imipenem/cilastatin-treated patients were cured at the test-of-cure assessment (12-37 days after therapy); in the microbiologic modified intent-to-treat population, cure rates were 81.7% (49 of 60) and 90.9% (50 of 55), respectively. The overall incidence of treatment-emergent adverse events was 80.4% for tigecycline vs. 53.9% after imipenem/cilastatin therapy (<it>P </it>< 0.001), primarily due to gastrointestinal-related events, especially nausea (21.6% vs. 3.9%; <it>P </it>< 0.001) and vomiting (12.4% vs. 2.0%; <it>P </it>= 0.005).</p> <p>Conclusions</p> <p>Clinical cure rates for tigecycline were consistent with those found in global cIAI studies. The overall safety profile was also consistent with that observed in global studies of tigecycline for treatment of cIAI, as well as that observed in analyses of Chinese patients in those studies; no novel trends were observed.</p> <p>Trial Registration</p> <p>ClinicalTrials.gov NCT00136201</p
Insight-HXMT dedicated 33-day observation of SGR J1935+2154 I. Burst Catalog
Magnetars are neutron stars with extreme magnetic field and sometimes
manifest as soft gamma-ray repeaters (SGRs). SGR J1935+2154 is one of the most
prolific bursters and the first confirmed source of fast radio burst (i.e. FRB
200428). Encouraged by the discovery of the first X-ray counterpart of FRB,
Insight-Hard X-ray Modulation Telescope (Insight-HXMT) implemented a dedicated
33-day long ToO observation of SGR J1935+2154 since April 28, 2020. With the
HE, ME, and LE telescopes, Insight-HXMT provides a thorough monitoring of burst
activity evolution of SGR J1935+2154, in a very broad energy range (1-250 keV)
with high temporal resolution and high sensitivity, resulting in a unique
valuable data set for detailed studies of SGR J1935+2154. In this work, we
conduct a comprehensive analysis of this observation including detailed burst
search, identification and temporal analyses. After carefully removing false
triggers, we find a total of 75 bursts from SGR J1935+2154, out of which 70 are
single-pulsed. The maximum burst rate is about 56 bursts/day. Both the burst
duration and the waiting time between two successive bursts follow log-normal
distributions, consistent with previous studies. We also find that bursts with
longer duration (some are multi-pulsed) tend to occur during the period with
relatively high burst rate. There is no correlation between the waiting time
and the fluence or duration of either the former or latter burst. It also seems
that there is no correlation between burst duration and hardness ratio, in
contrast to some previous reports. In addition, we do not find any X-ray burst
associated with any reported radio bursts except for FRB 200428.Comment: 31 pages, 10 figures, accepted for publication in ApJ
Robust estimation of bacterial cell count from optical density
Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data
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