A large circular transmitter (power pad) is often utilized for inductively wireless charging so that the power receiver can position itself freely within the power pad. However, the uneven magnetic ...field distribution leads to the impedance mismatch and the variable transferred power due to the misalignment between a receiving coil and a relatively large transmitter coil. In this paper, the effects of the turn numbers, trace spacing, and coil size on the uniformity of magnetic field distribution over a planar spiral coil (PSC) are investigated based on an analytical model. Then, the genetic algorithm is used to optimize the trace width and spacing of a ten-turn PSC with the fixed outer and inner diameters, whereas the magnetic field is numerically calculated by HFSS software. The geometrically optimal PSC is obtained with the trace width approximately equal to trace spacing for each turn by minimizing the coefficient of variation (COV) of magnetic field within an effective charging area over the coil. The results showed that the simulated and measured COVs of magnetic field were 0.130 and 0.121, respectively, which are obviously less than that of the uniformly spaced regular coil and show a little less than that of the optimally spaced coil with fixed trace width. Therefore, the trace spacing is a major consideration to achieve the uniform magnetic field, whereas the trace width variation is applied to refine the evenness of field. It is also expected that the proposed GA-based optimization is well applied to design other Txs with conformable shape in inductively WPT systems for stable power delivery regardless of the receiver positions.
Cohort evidence that links long-term exposures to air pollution and mortality comes largely from the United States and European countries. We investigated the relationship between long-term exposures ...to particulate matter <10μm in diameter (PM10), nitrogen dioxide (NO2), and sulfur dioxide (SO2) and mortality of lung cancer in Northern China. A cohort of 39,054 participants were followed during 1998–2009. Annual average concentrations for PM10, NO2, and SO2 were determined based on data collected from central monitoring stations. Lung cancer deaths (n=140) were obtained from death certificates, and hazard ratios (HRs) were estimated using Cox proportional hazards models, adjusting for age, gender, BMI, education, marital status, smoking status, passive smoking, occupation, alcohol consumption, etc. Each 10mg/m3 increase in PM10 concentrations was associated with a 3.4%–6.0% increase in lung cancer mortality in the time-varying exposure model and a 4.0%–13.6% increase in the baseline exposure model. In multi-pollutant models, the magnitude of associations was attenuated, most strongly for PM10. The association was different in men and women, also varying across age categories and different smoking status. Substantial differences exist in the risk estimates for participants based on assignment method for air pollution exposure.
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•The relationship between exposure to air pollution and lung cancer is proposed.•Levels of PM10 and SO2 were associated with lung cancer mortality independently.•The association was different in men and women, and varied across smoking status.
According to the special working condition in the commutation region of the traction grid, a novel technique of online core-loss measurement for the electric locomotive onboard traction transformer ...is proposed to noninvasively monitor the status of the magnetic core in real time. Meanwhile, a new modeling approach is also put forward for the equivalent nonlinear magnetizing inductance <inline-formula><tex-math notation="LaTeX">L_{M}</tex-math> </inline-formula> of the magnetic core. First, a no-load test under 31 kV is implemented on a healthy traction transformer, and the measured transient terminal voltages and currents are then filtered and downsampled by the comprehensive test and fault diagnosis system of electric locomotive traction transformer. Next, the magnetizing inductance <inline-formula><tex-math notation="LaTeX">L_{M}</tex-math></inline-formula> is modeled as the ratio of "the derivative of main flux linkage λ p with respect to time" over "the derivative of magnetizing current <inline-formula><tex-math notation="LaTeX">i_{m}</tex-math> </inline-formula> with respect to time." After that the proposed <inline-formula><tex-math notation="LaTeX"> L_{M}</tex-math></inline-formula> model is verified by comparing with the experimental results and two other models. Finally, the proposed technique for online estimation of core loss is applied on a normal onboard traction transformer and a downscaled testing transformer with different severity of interlaminar fault. The experimental results approximately match the theoretical calculation, and the online estimated values of core loss show sharply rising trend under incipient fault.
Current sharing among inductors is an important issue in both isolated and nonisolated dc-dc converters. In this paper, average current sharing is in-depth modeled and analyzed for both interleaved ...multiphase buck converters and isolated current-doubler dc-dc converters. The features and comparison of various current-sharing techniques used in isolated and nonisolated dc-dc converters are presented, and the corresponding design guidelines are provided based on the theoretical analysis. The analysis reveals that the state-of-the-art current-sharing technique for multiphase buck converters cannot be directly applied to isolated current-doubler rectifier (CDR) dc-dc converters to achieve balanced inductor currents. Passive and active current-sharing methods are proposed for isolated current-doubler dc-dc converters to balance two inductor currents. Experimental results are presented to verify the modeling analysis and the proposed current-sharing techniques for CDRs in isolated dc-dc converters.
The ready availability, low price and environmentally benign character of iron mean that it is an ideal alternative to precious metals in catalysis. Recent growth in the number of iron-catalysed ...reactions reported reflects an increasing demand for sustainable chemistry. Only a limited number of chiral iron catalysts have been reported and these have, in general, proven less enantioselective than other transition-metal catalysts, thus limiting their appeal. Here, we report that iron complexes of spiro-bisoxazoline ligands are highly efficient catalysts for asymmetric O-H bond insertion reactions. These complexes catalyse insertions into the O-H bond of a wide variety of alcohols and even water, with exceptional enantioselectivities under mild reaction conditions. The selectivities surpass those obtained with other transition-metal catalysts. This study should inspire and encourage the use of iron instead of traditional precious metals in the development of greener catalysts for catalytic asymmetric synthesis.
The symptoms of tracheobronchial foreign body in the elderly are not typical, so they are often missed or misdiagnosed. This study aims to depict the clinical characteristics of tracheobronchial ...foreign body inhalation in the elderly. We retrospectively analysed the clinical data of elder patients (age ≥ 65 years) diagnosed with tracheal and bronchial foreign bodies. The data included age, sex, clinical symptoms, type and location of foreign bodies, prehospital duration, Chest CT, bronchoscopic findings, and frequencies and tools for removing these elderly patients' tracheal and bronchial foreign bodies. All patients were followed up for a half year. Fifty-nine cases were included, of which only 32.2% had a definite aspiration history. Disease duration > 30 days accounted for 27.1% of the patients. 27.1% of the patients had a history of stroke, and 23.8% had Alzheimer's Disease. Regarding clinical symptoms, patients mainly experience cough and expectoration. The most common CT findings were abnormal density shadow (37.3%) and pulmonary infiltration (22.0%). Under bronchoscopy, purulent secretions were observed in 52.5% of patients, and granulation tissue hyperplasia was observed in 45.8%. Food (55.9%) was the most common foreign object, including seafood shells (5.1%), bones (20.3%), dentures (18.6%), and tablets (20.3%). The success rate of foreign body removal under a bronchoscope was 96.7%, 28.8% of the foreign bodies were on the left and 69.5% on the right. 5.1% of the elderly patients required rigid bronchoscopy, and 6.8% required two bronchoscopies. In elderly cohorts, tracheal foreign bodies are obscured by nonspecific clinical presentations and a paucity of aspiration history, challenging timely diagnosis. Predominantly constituted by food particles, with a notable predilection for the left bronchial tree, these cases demand skilled bronchoscopic management, occasionally requiring sophisticated approaches for successful extraction.
This article investigates using optical fibers with enhanced backscattering profiles to improve distributed fiber sensor performance and reduce instrumentation costs. Using a femtosecond (fs) laser ...direct writing technique, the Rayleigh backscattering profile of a standard telecom fiber was enhanced by more than 40 dB to improve the signal-to-noise ratio (SNR) for optical frequency domain reflectometry (OFDR). The enhanced backscattering signals enable effectively distributed strain measurements using a low-cost tunable laser (TL). Median filtering is applied to denoise cross correlation results to further improve measurement outcomes. Results presented in this article show that a TL with a 1-nm tuning range, which is far less than the tuning range used in commercial OFDR interrogators, can perform effectively distributed strain measurements using sensing fibers with enhanced backscattering profiles. The sensing fiber with over 40-dB backscattering enhancement achieved 4.8-cm spatial resolution in strain measurements with a root mean square accuracy of less than 2.70 <inline-formula> <tex-math notation="LaTeX">\mu \varepsilon </tex-math></inline-formula> when 10-50 <inline-formula> <tex-math notation="LaTeX">\mu \varepsilon </tex-math></inline-formula> were exerted to the sensing fiber. Results presented in this article reveal both the potential and limitations of sensing fibers with enhanced backscattering for OFDR-based distributed fiber sensors.
Background. Knee osteoarthritis (KOA) is a common disease in aged adults. Intra-articular (IA) injection of platelet-rich plasma (PRP) therapy is an effective minimally invasive treatment for KOA. We ...aimed to compare the efficacy and safety of platelet-rich plasma (PRP) with placebo or other conservative treatments. Methods. We conducted a meta-analysis to identify relevant articles from online register databases such as PubMed, Medline, Embase, and the Cochrane Library. The primary outcomes were the visual analogue scale (VAS) score, Western Ontario and McMaster Universities Arthritis Index (WOMAC) score, and International Knee Documentation Committee (IKDC) subjective score. The secondary outcome was the adverse event rate. Results. A total of 895 articles were identified, of which 23 randomized controlled trials that met the inclusion criteria were determined as eligible. Compared with placebo, PRP had a lower VAS score and higher IKDC subjective score at the 6th month after treatment and significantly less WOMAC score during the follow-up period. Compared with oral NSAIDs, PRP gained a lower WOMAC score at the 6th month after treatment. The VAS score decreased after treatment when reaching PRP and CS. As compared to the HA, the VAS score, WOMAC score, and IKDC subjective score all revealed better PRP results. There were no significant differences in adverse event rates comparing PRP versus placebo or HA. Different PRP applications did not show significant differences in VAS score in the 1st month and WOMAC score in the 3rd month after treatment. Conclusion. To compare with the conservative treatments mentioned above, PRP is more effective in relieving symptoms. There were no significant differences between triple PRP application and single PRP application in short-term curative effect.
This paper reports on the use of machine learning to delineate data harnessed by fiber-optic distributed acoustic sensors (DAS) using fiber with enhanced Rayleigh backscattering to recognize ...vibration events induced by human locomotion. The DAS used in this work is based on homodyne phase-sensitive optical time-domain reflectometry (φ-OTDR). The signal-to-noise ratio (SNR) of the DAS was enhanced using femtosecond laser-induced artificial Rayleigh scattering centers in single-mode fiber cores. Both supervised and unsupervised machine-learning algorithms were explored to identify people and specific events that produce acoustic signals. Using convolutional deep neural networks, the supervised machine learning scheme achieved over 76.25% accuracy in recognizing human identities. Conversely, the unsupervised machine learning scheme achieved over 77.65% accuracy in recognizing events and human identities through acoustic signals. Through integrated efforts on both sensor device innovation and machine learning data analytics, this paper shows that the DAS technique can be an effective security technology to detect and to identify highly similar acoustic events with high spatial resolution and high accuracies.
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