We consider the problem of target localization by a network of passive sensors. When an unknown target emits an acoustic or a radio signal, its position can be localized with multiple sensors using ...the time difference of arrival (TDOA) information. In this paper, we consider the maximum likelihood formulation of this target localization problem and provide efficient convex relaxations for this nonconvex optimization problem. We also propose a formulation for robust target localization in the presence of sensor location errors. Two Cramer-Rao bounds are derived corresponding to situations with and without sensor node location errors. Simulation results confirm the efficiency and superior performance of the convex relaxation approach as compared to the existing least squares based approach when large sensor node location errors are present.
In this letter, we propose a new approach to the localization problem in wireless sensor networks using received-signal-strength (RSS) measurements. The problem is reformulated under the equivalent ...exponential transformation of the conventional path loss measurement model and the unscented transformation (UT), and is approximately approached by the maximum likelihood (ML) parameter estimation, which we refer to as the weighted least squares (WLS) approach. This formulation is used for sensor node localization in both noncooperative and cooperative scenarios. Simulation results confirm the effectiveness of the approach for both outdoor and indoor environments.
It has been reported that the transmission of COVID-19 can be influenced by the variation of environmental factors due to the seasonal cycle. However, its underlying mechanism in the current and ...onward transmission pattern remains unclear owing to the limited data and difficulties in separating the impacts of social distancing. Understanding the role of seasonality in the spread of the COVID-19 pandemic is imperative in formulating public health interventions. Here, the seasonal signals of the COVID-19 time series are extracted using the EEMD method, and a modified Susceptible, Exposed, Infectious, Recovered (SEIR) model incorporated with seasonal factors is introduced to quantify its impact on the current COVID-19 pandemic. Seasonal signals decomposed via the EEMD method indicate that infectivity and mortality of SARS-CoV-2 are both higher in colder climates. The quantitative simulation shows that the cold season in the Southern Hemisphere countries caused a 59.71 ± 8.72% increase of the total infections, while the warm season in the Northern Hemisphere countries contributed to a 46.38 ± 29.10% reduction. COVID-19 seasonality is more pronounced at higher latitudes, where larger seasonal amplitudes of environmental indicators are observed. Seasonality alone is not sufficient to curb the virus transmission to an extent that intervention measures are no longer needed, but health care capacity should be scaled up in preparation for new surges in COVID-19 cases in the upcoming cold season. Our study highlights the necessity of considering seasonal factors when formulating intervention strategies.
•Infectivity and mortality of SARS-CoV-2 are both higher in colder climates.•Simulation indicates 40–60% COVID-19 cases are related to seasonality.•COVID-19 seasonality is more pronounced at higher latitudes.•Seasonality alone is not sufficient to curb the COVID-19 transmission.
Abstract Objectives To compare the methodological and reporting quality of systematic reviews by authors from China and those from the United States (USA). Study Design and Setting From systematic ...reviews of randomized trials published in 2014 in English, we randomly selected 100 from China and 100 from the USA. The methodological quality was assessed using the Assessing the Methodological Quality of Systematic Reviews (AMSTAR) tool, and reporting quality assessed using the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) tool. Results Compared with systematic reviews from the USA, those from China were more likely to be a meta-analysis, published in low-impact journals, and a non-Cochrane review. The mean summary Assessing the Methodological Quality of Systematic Reviews score was 6.7 (95% confidence interval: 6.5, 7.0) for reviews from China and 6.6 (6.1, 7.1) for reviews from the USA, and the mean summary Preferred Reporting Items for Systematic Reviews and Meta-analyses score was 21.2 (20.7, 21.6) for reviews from China and 20.6 (19.9, 21.3) for reviews from the USA. The differences in summary quality scores between China and the USA were statistically nonsignificant after adjusting for multiple review factors. Conclusion The overall methodological and reporting quality of systematic reviews by authors from China are similar to those from the USA, although the quality of systematic reviews from both countries could be further improved.
Although the relationship between asthma and exposure to fine particulate matter (PM2.5) has been frequently measured, reported conclusions have not been consistent. As emergency department (ED) ...visits are an effective way to estimate health outcomes for people with asthma and short-term exposure to PM2.5, this review systematically searched five databases without language or geographical restrictions from inception to January 13, 2015 to study the impact of PM2.5 on asthma ED visits. A random-effects model was used to calculate the pooled risk ratio (RR) and 95 % confidence intervals (CI). With respect to short-term effects, asthma ED visits increased at higher PM2.5 concentrations (RR 1.5 % per 10 μg/m³; 95 % CI 1.2–1.7 %), and children were more susceptible (3.6 % per 10 μg/m³; 95 % CI 1.8, 5.3 %) than adults (1.7, 95 % CI 0.7 %, 2.8 %) to increased PM2.5; the ED visits increased during the warm season by 3.7 % (95 % CI 0.5, 6.9 %) per 10 μg/m³ increase in PM2.5, which was higher than the corresponding increase during the cold season (2.6, 95 % CI 0.7–4.6 %). This demonstrates that ambient PM2.5 has an adverse impact on asthma ED visits after short-term exposure and that children are a high-risk population when PM2.5 concentrations are high, particularly in warm seasons, during which measures should be taken to prevent PM2.5.
Purpose/Significance It is the requirement of the present times to build an independent knowledge system of evidence-based digital humanistic paradigm with Chinese characteristics. Method/Process ...Based on the World 3 theory developed by Popper, this study defines the essence of digital humanities research as representing, revealing and reproducing the structure of the objective knowledge world. Furthermore, based on the paradigm theory developed by Kuhn, this paper deeply discusses the basic theoretical elements of the independent knowledge system of the evidence-based digital humanities paradigm with Chinese characteristics. In this paper, the carding of the elements of evidence-based digital humanities theory is carried out from the perspective of the scientific community of digital humanities research. That is to say, the research that adheres to the evidence-based ideology and method of digital humanity is identified as the same research community, and it is believed that evidence-based digital humani
Growing evidence indicates that insomnia may be associated with mortality. However, these findings have been inconsistent. We systematically searched MEDLINE and EMBASE to identify prospective cohort ...studies that assessed the association between insomnia disorder/individual insomnia symptoms and the risk of mortality among adults aged ≥18 yrs. We addressed this association using summary hazard ratios (HRs) and 95% confidence intervals (CIs) calculated using random-effects meta-analysis, and the GRADE approach to rate the certainty of evidence. Twenty-nine cohorts including 1,598,628 individuals (55.3% men; mean age 63.7 yrs old) with a median follow-up duration of 10.5 yrs proved eligible. Difficulty falling asleep (DFA) and non-restorative sleep (NRS) were associated with an increased risk of all-cause mortality (DFA: HR = 1.13, 95%CI 1.03 to 1.23, p = 0.009, moderate certainty; NRS: HR = 1.23, 95%CI 1.07 to 1.42, p = 0.003, high certainty) and cardiovascular disease mortality (DFA: 1.20, 95%CI: 1.01, 1.43; p = 0.04, moderate certainty; NRS: HR = 1.48, 95%CI 1.06 to 2.06, p = 0.02, moderate certainty). Convincing associations between DFA and all-cause mortality were restricted to the mid to older-aged population (moderate credibility). Insomnia disorder, difficulty maintaining sleep, and early morning awakening proved to be unassociated with all-cause and cardiovascular disease mortality. No insomnia symptoms proved to be associated with cancer-related mortality.
Selective harmonic elimination (SHE) technology has been widely used in many medium- and high-power converters which operates at very low switching frequency; however, it is still a challenging work ...to solve the switching angles from a group of nonlinear transcendental equations, especially for the multilevel converters. Based on the Groebner bases and symmetric polynomial theory, an algebraic method is proposed for SHE. The SHE equations are transformed to an equivalent canonical system which consists of a univariate high-order equations and a group of univariate linear equations, thus the solving procedure is simplified dramatically. In order to solve the final solutions from the definition of the elementary symmetric polynomials, a univariate polynomial equation is constructed according to the intermediate solutions and two criteria are given to check whether the results are true or not. Unlike the commonly used numerical and random searching methods, this method has no requirement on choosing initial values and can find all the solutions. Compared with the existing algebraic methods, such as the resultant elimination method, the calculation efficiency is improved, and the maximum solvable switching angles is nine. Experiments on three-phase two-level and 13-level inverters verify the correctness of the switching angles solved by the proposed method.
Neoadjuvant chemotherapy (NAC) has become an essential treatment for breast cancer. However, there is still no consensus on the best tool to evaluate pathological response to NAC.
Two reviewers ...systematically searched Cochrane, PubMed, EMBASE, Web of Science, and CBM (last updated in February 2017) for eligible articles. We independently screened and selected studies that conformed to the inclusion criteria and extracted the requisite data. Pooled sensitivity, specificity, and the area under the SROC curve were calculated to estimate the diagnostic accuracy of magnetic resonance imaging (MRI) and positron emission computed tomography (PET/CT). And the relative DOR (RDOR) was used to compare accuracy for levels of the covariable.
Thirteen studies involving 575 patients who underwent MRI and 618 who underwent PET/CT were included in our analysis. The pooled sensitivity and specificity of MRI were 0.88 (95% CI: 0.78–0.94) and 0.69 (95% CI: 0.51–0.83), respectively. The corresponding values for PET/CT were 0.77 (95% CI: 0.58–0.90) and 0.78 (95% CI: 0.63–0.88), respectively. The area under the SROC curve for MRI and PET/CT were 0.88 and 0.84, respectively. And the RDOR = 1.44 (95% CI, 0.46–4.47 P = 0.83).
MRI had a higher sensitivity and PET/CT had a higher specificity in predicting the pathologic response after NAC in patients with breast cancer. According to the area under the SROC curve and anatomic discriminative resolution, MRI is the more suitable recommendation for predicting the pathologic response after NAC.
•We compared the accuracy of MRI and PET/CT predicting pathological response after neoadjuvant chemotherapy in breast cancer.•Compared with PET/CT, MRI had a higher sensitivity but lower specificity in predicting the pathologic response.•MRI is the more suitable recommendation for predicting the pathologic response after neoadjuvant chemotherapy.
Abstract Objective Network meta-analyses (NMAs) aim to rank the benefits (or harms) of interventions, based on all available randomized controlled trials. Thus, the identification of relevant data is ...critical. We assessed the conduct of the literature searches in NMAs. Study Design Published NMAs were retrieved by searching electronic bibliographic databases and other sources. Two independent reviewers selected studies and five trained reviewers abstracted data regarding literature searches, in duplicate. Search method details were examined using descriptive statistics. Results Two hundred forty-nine NMAs were included. Eight used previous systematic reviews to identify primary studies without further searching, and five did not report any literature searches. In the 236 studies that used electronic databases to identify primary studies, the median number of databases was 3 (interquartile range: 3–5). MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials were the most commonly used databases. The most common supplemental search methods included reference lists of included studies (48%), reference lists of previous systematic reviews (40%), and clinical trial registries (32%). None of these supplemental methods was conducted in more than 50% of the NMAs. Conclusion Literature searches in NMAs could be improved by searching more sources, and by involving a librarian or information specialist.
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