Robust and Efficient Frequency Estimator for Undersampled Waveforms Based on Frequency Offset Recognition.

This paper proposes an efficient frequency estimator based on Chinese Remainder Theorem for undersampled waveforms. Due to the emphasis on frequency offset recognition (i.e., frequency shift and compensation) of small-point DFT remainders, compared to estimators using large-point DFT remainders, it can achieve higher noise robustness in low signal-to-noise ratio (SNR) cases and higher accuracy in high SNR cases. Numerical results show that, by incorporating a remainder screening method and the Tsui spectrum corrector, the proposed estimator not only lowers the SNR threshold of detection, but also provides a higher accuracy than the large-point DFT estimator when the DFT size decreases to 1/90 of the latter case

Pouzdanost i osjetljivost pokazatelja povezanih s procjenom kardiovaskularnih funkcionalnih sposobnosti

Determining the recovery heart rate (RHR) index after various submaximal exercises is a popular and practical way for a population’s cardiovascular fitness evaluation. These evaluations are based on the regression among RHR, load intensity, and maximal oxygen uptake. However, little work has been done to 1) explore the influences of body weight and height on these tests’ reliability and sensitivity, and 2) compare the reliability among the tests. As a result, practitioners often choose tests without the appropriate criteria. This study researched the mentioned two aspects by evaluating 30 male college students via three common tests – 30 cm step test, 40 cm step test and squat-up-down test. The results showed that the reliability and sensitivity of the three tests were remarkably different. Adding body weight into the evaluation would improve both reliability and sensitivity. Considering all the influence factors, 30 cm step test was the best one. These findings suggested that applying the relative RHR index (normalized by body weight) should be considered for a population’s cardiovascular fitness evaluation in the future.Uvod Opće je poznato da razina kondicijske pripremljenosti ovisi o dobi, spolu, rasi, antropometrijskim mjerama (tjelesnoj težini i visini) te intenzitetu treninga ili vježbanja. Već desetljećima sportski znanstvenici pokušavaju pronaći pouzdane načine za njezino vrednovanje na raznim selektiranim populacijama. Kao rezultat tih istraživanja, danas postoje brojne metode za utvrđivanje stanja kondicijske pripremljenosti koje su se pokazale primjerene ili za opću populaciju ili za sportaše različite dobi. Popularan i praktičan način za procjenu kardiovaskularnih sposobnosti jest utvrđivanje indeksa frekvencije srca u oporavku (RHR) nakon različitih sub-maksimalnih optrećenja. Ove procjene temelje se na regresiji između RHR, intenziteta opterećenja i maksimalnog primitka kisika (VO2max). Ipak, vrlo malo znanstvenih istraživanja bilo je usmjereno na utvrđivanje: 1) utjecaja tjelesne težine i visine na pouzdanost i osjetljivost tih mjernih instrumenta i 2) na usporedbu koeficijenata pouzdanosti između testova. Kao posljedica toga, u praksi se izabiru i upotrebljavaju testovi bez odgovarajućih kriterija. Cilj je ove studije istražiti navedene aspekte utvrđivanjem stanja kondicijske pripremljenosti 30 studenata primjenom tri slična testa – step test na klupici visine 30 cm, step test na klupici visine 40 cm i čučnjevi. Metode Ispitanici su dobi 20,3±,2 godine, tjelesne težine 64,0±2,0 kg i visine 173,4±,9 centimetara. Svi ispitanici bili su prosječni studenti tjelesnog odgoja koji se nisu aktivno bavili sportom. Koeficijenti pouzdanosti za sve mjerne instrumente utvrđeni su formulom Thomasa i Nelsona (2001) u kojoj MSs predstavlja aritmetičku sredinu kvadrata rezultata ispitanika (varijanca pravih rezultata), a MSE aritmetičku sredinu kvadrata pogreške (varijanca pogreške ili standardna pogreška mjerenja). Sve MS vrijednosti (sume kvadrata rezultata ili zajedničke varijance rezultata) dobivene su analizom varijance (ANOVA) za svaki paralelni test. Razina značajnosti za sve testove postavljena je na razinu od 0,05. Za obradu podataka korišten je program SPSS 10 za Windowse (SPSS Inc, Chicago, IL, USA). Rezultati i rasprava Rezultati istraživanja pokazali su da su pouzdanost i objektivnost ispitivana tri testa statistički značajno različiti. Normaliziranjem rezultata s koeficijentom tjelesne težine povećala bi se i pouzdanost i osjetljivost mjernih instrumenata. Uzimajući u obzir sve faktore koji utječu na pouzdanost i osjetljivost mjernih instrumenata, pokazalo se da je najbolji od testiranih testova step test na klupici visine 30 cm. Ovi rezultati ukazuju na činjenicu da bi se relativni indeks frekvencije srca u oporavku RHR (normaliziran tjelesnom težinom ispitanika) trebao u budućnosti koristiti za utvrđivanje kardiovaskularne sposobnosti ispitanika, osobito u populacijskim mjerenjima

Identification and Risk Characteristics of Agricultural Drought Disaster Events Based on the Copula Function in Northeast China

Accurate feature identification of drought disaster events is required for proper risk management in agriculture. This study improved the crop water deficit index (CWDI) by including the daily meteorological, crop development stage, soil moisture content, and yield data for 1981–2020 in northeastern China. Two drought characteristic variables (drought duration and intensity) were extracted using the theory of runs to produce the improved crop water deficit index (CWDIwp). Thresholds for the bivariate indicators were also determined for agricultural drought events of varying severity. A joint distribution model for drought variables was constructed based on five types of Archimedean copulas. The joint probability and the joint recurrence period for agricultural drought events were analyzed for drought events with varying intensities in northeast China. The results suggest that the CWDIwp can reliably identify the onset, duration, and intensity of drought events over the study area and can be used to monitor agricultural drought events. The conditional probability of drought intensity (duration) decreased as the drought duration (intensity) threshold increased, whereas the drought recurrence period increased as the threshold for drought duration and intensity rose. In the period (1981–2020), drought intensity in the three Northeastern provinces showed an increasing trend in the order Jilin Province > Liaoning Province > Heilongjiang Province. The spatial distribution of the joint probability and the joint recurrence period was obvious, and the joint probability showed a decreasing distribution trend from west to east. The distribution trend for the joint probability was opposite to that of the joint recurrence period. Furthermore, the areas with high drought probability values corresponded to the areas with low values for the recurrence period, indicating that the drought occurrence probability was higher, and the recurrence period value was lower in the drought-prone areas. The high-risk drought areas (60–87%) were in western Liaoning and western Jilin, with a recurrence period of 1–3 years, whereas the low-risk areas ( moderate drought > severe drought > extreme drought. The order for the recurrence period was light drought < moderate drought < severe drought < extreme drought. The results provide technical support for disaster prevention and mitigation in drought risk management

Identification and Risk Characteristics of Agricultural Drought Disaster Events Based on the Copula Function in Northeast China

Accurate feature identification of drought disaster events is required for proper risk management in agriculture. This study improved the crop water deficit index (CWDI) by including the daily meteorological, crop development stage, soil moisture content, and yield data for 1981&ndash;2020 in northeastern China. Two drought characteristic variables (drought duration and intensity) were extracted using the theory of runs to produce the improved crop water deficit index (CWDIwp). Thresholds for the bivariate indicators were also determined for agricultural drought events of varying severity. A joint distribution model for drought variables was constructed based on five types of Archimedean copulas. The joint probability and the joint recurrence period for agricultural drought events were analyzed for drought events with varying intensities in northeast China. The results suggest that the CWDIwp can reliably identify the onset, duration, and intensity of drought events over the study area and can be used to monitor agricultural drought events. The conditional probability of drought intensity (duration) decreased as the drought duration (intensity) threshold increased, whereas the drought recurrence period increased as the threshold for drought duration and intensity rose. In the period (1981&ndash;2020), drought intensity in the three Northeastern provinces showed an increasing trend in the order Jilin Province &gt; Liaoning Province &gt; Heilongjiang Province. The spatial distribution of the joint probability and the joint recurrence period was obvious, and the joint probability showed a decreasing distribution trend from west to east. The distribution trend for the joint probability was opposite to that of the joint recurrence period. Furthermore, the areas with high drought probability values corresponded to the areas with low values for the recurrence period, indicating that the drought occurrence probability was higher, and the recurrence period value was lower in the drought-prone areas. The high-risk drought areas (60&ndash;87%) were in western Liaoning and western Jilin, with a recurrence period of 1&ndash;3 years, whereas the low-risk areas (&lt;40%) were located in the mountainous areas of eastern Liaoning and eastern Jilin. The joint probability and joint recurrence period for agricultural drought events of varying severity were quite different, with the probability following the order light drought &gt; moderate drought &gt; severe drought &gt; extreme drought. The order for the recurrence period was light drought &lt; moderate drought &lt; severe drought &lt; extreme drought. The results provide technical support for disaster prevention and mitigation in drought risk management

DFT spectra of different frequency shift cases.

<p>DFT spectra of different frequency shift cases.</p

RMSE comparison among different CRT-based estimators.

<p>RMSE comparison among different CRT-based estimators.</p

Normalized magnitude of peak bin versus <i>δ_i</i>.

<p>Normalized magnitude of peak bin versus <i>δ_i</i>.</p

Detection probability curves of different CRT-based estimators.

<p>Detection probability curves of different CRT-based estimators.</p

Efficacy and Safety of Botulinum Toxin Type A for Limb Spasticity after Stroke: A Meta-Analysis of Randomized Controlled Trials

Background. Inconsistent data have been reported for the effectiveness of intramuscular botulinum toxin type A (BTXA) in patients with limb spasticity after stroke. This meta-analysis of available randomized controlled trials (RCTs) aimed to determine the efficacy and safety of BTXA in adult patients with upper and lower limb spasticity after stroke. Methods. An electronic search was performed to select eligible RCTs in PubMed, Embase, and the Cochrane library through December 2018. Summary standard mean differences (SMDs) and relative risk (RR) values with corresponding 95% confidence intervals (CIs) were employed to assess effectiveness and safety outcomes, respectively. Results. Twenty-seven RCTs involving a total of 2,793 patients met the inclusion criteria, including 16 and 9 trials assessing upper and lower limb spasticity cases, respectively. For upper limb spasticity, BTXA therapy significantly improved the levels of muscle tone (SMD=-0.76; 95% CI -0.97 to -0.55; P<0.001), physician global assessment (SMD=0.51; 95% CI 0.35-0.67; P<0.001), and disability assessment scale (SMD=-0.30; 95% CI -0.40 to -0.20; P<0.001), with no significant effects on active upper limb function (SMD=0.49; 95% CI -0.08 to 1.07; P=0.093) and adverse events (RR=1.18; 95% CI 0.72-1.93; P=0.509). For lower limb spasticity, BTXA therapy was associated with higher Fugl-Meyer score (SMD=5.09; 95%CI 2.16-8.01; P=0.001), but had no significant effects on muscle tone (SMD=-0.12; 95% CI -0.83 to 0.59; P=0.736), gait speed (SMD=0.06; 95% CI -0.02 to 0.15; P=0.116), and adverse events (RR=1.01; 95% CI 0.71-1.45; P=0.949). Conclusions. BTXA improves muscle tone, physician global assessment, and disability assessment scale in upper limb spasticity and increases the Fugl-Meyer score in lower limb spasticity