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1.
《Advanced Powder Technology》2022,33(8):103663
In this work, a new type of FeSi/FeNi soft magnetic powder core (SMPC) was successfully fabricated by coating FeNi nanoparticles on the surface of FeSi micrometer powder. The effects of different contents of FeNi nanoparticles on the micromorphology, internal structures, and soft magnetic properties of SMPCs were studied. The results show that FeNi nanoparticles adhere to the surface of FeSi powder, which can effectively fill the air gap between FeSi powder and is beneficial to the compaction of the powder cores during the pressing process. Thus, the density of the SMPCs is increased. Compared to FeSi SMPCs, the comprehensive soft magnetic properties of FeSi/FeNi SMPCs have been greatly improved. When adding 15 wt% FeNi nanoparticles, the SMPCs exhibit excellent magnetic properties with high effective permeability (increased by 43.8 %) and low core loss (decreased by 22.1 %). The high performance FeSi/FeNi SMPCs prepared in this work are expected to be widely used in power choke coils, uninterruptible power supplies, and boosts and inverter inductors. 相似文献
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目的 了解武汉市一般人群血清中全氟及多氟烷基化合物(PFASs)浓度,探索血清中PFASs浓度水平的影响因素。方法 以在武汉市某医院进行一般体检的人群为研究对象(n=67),通过超高效液相色谱-三重四级杆质谱(UPLC-TQ/MS)联用仪测定外周血清中12种PFASs浓度,采用多元线性回归分析方法分析一般人口学特征和血清中PFASs浓度的关联性。结果 武汉市一般人群血清中12种PFASs的平均浓度水平为11.60 ng/mL。全氟辛烷磺酸及其盐类(PFOS)和全氟辛酸及其盐类(PFOA)的贡献率较大,分别为45.03%和31.86%。男性人群血清中PFOS、PFOA、全氟己基磺酸(PFHxS)、全氟壬酸(PFNA)等主要化合物的浓度高于女性,其β值(95%可信区间)分别为0.708(0.313,1.104)、0.518(0.069,0.967)、0.724(0.388,1.059)和0.684(0.399,0.968)。同时,发现血清中PFOS、PFHxS、PFNA浓度和年龄呈正相关,其β值(95%可信区间)分别为0.062(0.042,0.081)、0.035(0.019,0.052)和0.030(0.016,0.045)。结论 性别和年龄对血清中PFASs浓度有影响,在进行人体PFASs暴露评估中应考虑这些因素。 相似文献
4.
《Cities》2019
Although the causes of asthma are inconclusive, it is fairly known that exposure to outdoor air pollutants can cause asthma, especially children's asthma morbidity. Whereas transportation is one of the major sectors that generate air pollutants, previous research that investigates the correlation between transportation and asthma narrowly focuses on the contribution of automobile traffic to children's asthma. Developing three spatial regression models (a spatial lag (SL) model, a spatial error (SE) model, and a general spatial (SAC) model), this paper investigates the roles of a variety of transportation factors in two distinct stages of children's asthma morbidity; asthma and severe asthma. With consideration to asthma-related socio-economic factors in the City of Seoul, the SE (R2 = 0.31) and SAC (R2 = 0.34) models consistently indicate that three out of four transportation factors associate with children's severe asthma at statistically significant level. They include the negative influence of bus transit and dense intersections, and the positive influence of active transportation activities on children's asthma severity. Interestingly, however, no significant contribution of transportation factors to children's asthma morbidity was identified by the SE (R2 = 0.29) and SAC (R2 = 0.28) models. Shedding more light on the complexity of children's asthma morbidity and severity, this paper proposes collaborative partnerships not only among multi- dimensional agencies, but also among multi-level government organizations. 相似文献
5.
《Ceramics International》2021,47(24):34695-34703
Li4x/3Zn2–2xTi1+2x/3O4 microwave dielectric ceramics with a spinel phase were prepared via a high-temperature solid-phase method. P–V–L theory, vibration spectra, and XPS were utilized to establish the links between the intrinsic and extrinsic factors and the microwave dielectric properties. According to the characterization, the change in permittivity (εr) was ascribed to the increase in the average bond ionicity of Ti–O(AfiTi-O) and the polar mode of the lattice vibration; the change in quality factor(Q × f) resulted from the change in the Ti–O lattice energy (AUTi-O) and existence of oxygen vacancy; the increase in temperature coefficient of the resonance frequency (τf) was triggered by the increase in the Ti–O bond energy. The Li0.6Zn1.1Ti1.3O4 ceramics (x = 0.45) sintered at 1125 °C finally obtained optimal microwave dielectric constants of εr = 17.3, Q × f = 76,318 GHz and τf = -58 ppm/°C. 相似文献
6.
Yifan Zhang Shaowei Bo Tao Feng Xialing Qin Yilin Wan Shanshan Jiang Chunxiao Li Jing Lin Tianfu Wang Xin Zhou Zhong‐Xing Jiang Peng Huang 《Advanced materials (Deerfield Beach, Fla.)》2019,31(21)
To design a clinically translatable nanomedicine for photodynamic theranostics, the ingredients should be carefully considered. A high content of nanocarriers may cause extra toxicity in metabolism, and multiple theranostic agents would complicate the preparation process. These issues would be of less concern if the nanocarrier itself has most of the theranostic functions. In this work, a poly(ethylene glycol)‐boron dipyrromethene amphiphile (PEG‐F54‐BODIPY) with 54 fluorine‐19 (19F) is synthesized and employed to emulsify perfluorohexane (PFH) into a theranostic nanoemulsion (PFH@PEG‐F54‐BODIPY). The as‐prepared PFH@PEG‐F54‐BODIPY can perform architecture‐dependent fluorescence/photoacoustic/19F magnetic resonance multimodal imaging, providing more information about the in vivo structure evolution of nanomedicine. Importantly, this nanoemulsion significantly enhances the therapeutic effect of BODIPY through both the high oxygen dissolving capability and less self‐quenching of BODIPY molecules. More interestingly, PFH@PEG‐F54‐BODIPY shows high level of tumor accumulation and long tumor retention time, allowing a repeated light irradiation after a single‐dose intravenous injection. The “all‐in‐one” photodynamic theranostic nanoemulsion has simple composition, remarkable theranostic efficacy, and novel treatment pattern, and thus presents an intriguing avenue to developing clinically translatable theranostic agents. 相似文献
7.
目的分离脊髓灰质炎病毒Ⅲ型Sabin株(sPVⅢ)C抗原和D抗原,并分析其部分特性。方法采用CsCl密度梯度离心法分离sPVⅢ的C抗原和D抗原,电镜观察病毒形态;SDS-PAGE检测病毒结构蛋白组成;微量BCA法检测蛋白浓度,计算每种抗原所占比例;细胞病变法检测病毒滴度。同时检测上样浓度及超离次数对C抗原纯度的影响。结果sPVⅢC抗原和D抗原在透射电镜下均呈球形,C抗原病毒颗粒密度较小,外壳大多较为松散,D抗原病毒颗粒密度较大,结构更稳固;C抗原由VP0、VP1、VP3蛋白组成,D抗原由VP1、VP2、VP3和VP4蛋白组成;C抗原和D抗原分别约占总蛋白含量的10%和90%,部分C抗原在分离前及分离过程中易产生聚集;D抗原的病毒滴度高于C抗原。降低上样浓度及进行二次超离可提高C抗原纯度。结论采用CsCl密度梯度离心法成功分离了sPVⅢ的C抗原和D抗原,C抗原滴度远低于D抗原,且部分易产生聚集,较难达到较高纯度。 相似文献
8.
《International Journal of Hydrogen Energy》2020,45(15):8456-8465
Two precursors, namely, p-CFO-T (tetragonal) and p-CFO-C (cubic), were fabricated by a sol-gel method via citric acid and poly(vinyl alcohol) complexation, respectively. After H2-reduction, the two were converted to Cu/Fe3O4 catalysts of different complexions, which are named as CFO-CA and CFO-PVA, respectively. The distribution of Fe2+ and Fe3+ in the Cu/Fe3O4 catalysts was studied by Raman and XPS techniques. It was disclosed that the distribution of Fe2+ and Fe3+ in Fe3O4 has an effect on Cu–Fe3O4 interaction and catalyst surface basicity. Compared to CFO-PVA, CFO-CA has a larger amount of Fe3+, which mostly sits at the octahedral sites, leading to stronger Cu–Fe3O4 interaction, and a larger amount of catalyst surface sites that are of weak basicity. As a result, the critical elementary steps of WGS reaction, viz. water dissociation, –COOH decomposition and CO2 desorption are promoted as reflected in the lower Ea and higher catalytic activity of CFO-CA. 相似文献
9.
《International Journal of Hydrogen Energy》2020,45(3):2257-2278
The uniform temperature distribution of a cross-flow planar solid oxide fuel cell (SOFC) stack plays an essential role in stack thermal safety and electrical property. However, because of the strict requirements in stack sealing struture, it is hard to acquire the temperature inside the stack using thermal detection devices within an acceptable cost. Therefore, accurately estimating the two-dimensional (2-D) temperature distribution of the cross-flow stack is crucial for its thermal management. In this paper, Firstly, a 2-D mechanism model of a cross-flow planar SOFC stack is established. The stack is divided into 5*5 nodes along the gas flow directions, which can reflect the stack states with moderate computational burden. Then, experimental test data is utilized to modify and validate the stack model, guaranteeing the model accuracy as well as the reliability of model-based state estimator design. Finally, easily-measured stack inputs and outputs are selected, and a temperature distribution estimator combined with unscented kalman filter (UFK) approach is developed to achieve accurate and fast temperature distribution estimation of a cross-flow SOFC stack. Simulation results demonstrate that the UKF-based temperature distribution estimator can precisely and quickly achieve the temperature distribution estimation of the cross-flow stack under both static state and dynamic state changes and is applicable to cross-flow stacks with different size or cell number as well, the maximum estimated absolute error is less than 0.15 K with an absolute error rate of 0.015%, which indicates the developed estimator has good estimation performances. 相似文献
10.
《Journal of the European Ceramic Society》2020,40(13):4578-4588
Trivalent erbium ions doped Bi2O3-B2O3 transparent glass ceramics containing CaF2 were prepared and characterized through X -ray diffraction, scanning electron microscopy, Fourier transform infrared absorption, optical absorption, and near infrared emission for 1.53 μm fiber lasers. The glass ceramics obtained by applying thermal treatment at 575 °C for 5 h and 575 °C for 10 h contain Bi3B5O12 and CaF2 crystallites. The Judd-Ofelt theory was applied to evaluate various spectroscopic and laser characteristic properties. The NIR emission corresponding to the 4I13/2 → 4I15/2 (∼1.53 μm) transition was studied by exciting the samples at 514.5 nm laser radiation. The stimulated emission cross-sections of ∼1.53 μm luminescence were also obtained applying the Mc Cumber theory. The experimental results confirm that the transparent glass ceramic obtained at a thermal treatment of 575 °C for 10 h is more suitable to design fiber lasers for diverse applications in the fields of industry, medicine and scientific research. 相似文献