MEMS interdigitated electrode pattern optimization for a unimorph piezoelectric beam

This paper presents optimization of interdigitated (d ₃₃ ) piezoelectric MEMS unimorph cantilever beams for harvesting vibration energy or for tuning resonators. The analysis of the poling behavior of the piezoelectric material is the key feature. While it is common that simplified models of interdigitated piezoelectric devices assume some uniform and well-defined poling pattern, the finite element modeling used in this work shows that not to be the case. A percent poling factor is developed to investigate the real losses associated with non-uniform poling. A parametric study in terms of electrode patterns, piezoelectric layer dimensions, and electrode dimensions is carried out to examine their effect on the percent poling factor. Design guidelines are provided to help ensure that such piezoelectric MEMS devices are developed to obtain optimum energy harvesting or tuning performance.     

Solvothermal synthesis of monodisperse ultrasmall cubic-structure Ba2YbF7 nanocrystals with intense upconversion

A series of monodisperse ultrasmall Ba₂YbF₇ nanocrystals with intense upconversion emission were synthesized via a facile solvothermal method by using oleic acid as capping ligands. X-ray diffraction (XRD) and transmission electron microscopy (TEM) assays revealed that the as-synthesized Ba₂YbF₇ nanocrystals are of cubic structure, rather than the reported tetragonal structure. The cell parameter of the particles is 5.918 Å. The Er³⁺ or Tm³⁺ doped Ba₂YbF₇ nanocrystals with the size of sub-10 nm can give an intense upconversion emission under the 980 nm laser excitation and the upconversion processes were discussed. The Ba₂YbF₇ nanocrystals show a potential application as a bioimaging agent.     

Dielectric properties and bright red emission of Y3+/Eu3+-codoped ZrO2 thin films prepared by chemical solution deposition

We report on an effective combination of good dielectric properties with bright red emission in Y³⁺/Eu³⁺-codoped ZrO₂ thin films. The thin films were deposited on fused silica and Pt/TiO₂/SiO₂/Si substrates using a chemical solution deposition method. The crystal structure, surface morphology, electrical and optical properties of the thin films were investigated in terms of annealing temperature, and Y³⁺/Eu³⁺ doping content. The 5%Eu₂O₃–3%Y₂O₃–92%ZrO₂ thin film with 400 nm thickness annealed at 700 °C exhibits optimal photoluminescent properties and excellent electrical properties. Under excitation by 396 nm light, the thin film on fused silica substrate shows bright red emission bands centered at 593 nm and 609 nm, which can be attributed to the transitions of Eu³⁺ ions. Dielectric constant and dissipation factor of the thin films at 1 kHz are 30 and 0.01, respectively, and the capacitance density is about 65.5 nf/cm² when the bias electric field is less than 500 kV/cm. The thin films also exhibit a low leakage current density and a high optical transmittance with a large band gap.     

Quantitative Analysis of Phytosterols in Edible Oils Using APCI Liquid Chromatography–Tandem Mass Spectrometry

Previous methods for the quantitative analysis of phytosterols have usually used GC–MS and require elaborate sample preparation including chemical derivatization. Other common methods such as HPLC with absorbance detection do not provide information regarding the identity of the analytes. To address the need for an assay that utilizes mass selectivity while avoiding derivatization, a quantitative method based on LC–tandem mass spectrometry (LC–MS–MS) was developed and validated for the measurement of six abundant dietary phytosterols and structurally related triterpene alcohols including brassicasterol, campesterol, cycloartenol, β-sitosterol, stigmasterol, and lupeol in edible oils. Samples were saponified, extracted with hexane and then analyzed using reversed phase HPLC with positive ion atmospheric pressure chemical ionization tandem mass spectrometry and selected reaction monitoring. The utility of the LC–MS–MS method was demonstrated by analyzing 14 edible oils. All six compounds were present in at least some of the edible oils. The most abundant phytosterol in all samples was β-sitosterol, which was highest in corn oil at 4.35 ± 0.03 mg/g, followed by campesterol in canola oil at 1.84 ± 0.01 mg/g. The new LC–MS–MS method for the quantitative analysis of phytosterols provides a combination of speed, selectivity and sensitivity that exceed those of previous assays.     

复合型潜流人工湿地处理漓江流域农村生活污水的研究

采用复合型潜流人工湿地对漓江流域农村生活污水进行处理,考察了其对SS、COD、氨氮、TN和TP的去除效果,并且对人工湿地生物相进行分析。结果表明,湿地内植物生长状况良好,栽种培育1个月后即可连续满负荷进水。稳定运行后,人工湿地对SS、COD、氨氮、TN和TP的平均去除率分别超过40%、70%、70%、90%和85%,出水可达GB 18918-2002的一级B排放要求。对人工湿地的生物相进行分析,可观察到有原生动物、后生动物和藻类,说明此时人工湿地系统已经比较成熟。     

Relationship between Serum Osteocalcin Levels and Non-Alcoholic Fatty Liver Disease in Adult Males,South China

AIM

To determine serum osteocalcin levels in South Chinese males with non-alcoholic fatty liver disease (NAFLD) and to examine the relation between serum osteocalcin and NAFLD.

METHODS

Data were collected from 1683 men attending the Fangchenggang Area Male Healthy and Examination Survey (FAMHES) from September 2009 to December 2009. Serum osteocalcin was measured with electrochemiluminescence immunoassay. An abdominal ultrasonographic examination for all individuals was performed by two experienced ultrasonographers. The associations of serum osteocalcin with NAFLD were evaluated.

RESULTS

The levels of serum osteocalcin were lower in 364 NAFLD participants than in 1319 non-NAFLD participants (24.51 ± 1.38 ng/mL vs. 20.81 ± 1.33 ng/mL, p < 0.001). Serum osteocalin level was associated with the scale of NAFLD (r = −0.150, p < 0.01). Serum osteocalin level tended to decrease with the scale of NAFLD. Binary logistic regression analysis showed that decreased ORs for NAFLD were observed from the first to the fourth osteocalcin quartiles.

CONCLUSIONS

Our findings suggest that a lower serum osteocalcin level is associated with the presence of NAFLD.     

直流X射线模拟电缆X射线响应的可行性

本文对电缆X射线辐照响应的机理和模拟方法进行了研究,分析了电缆直流和脉冲X射线辐照响应的异同。建立了带状电缆X射线辐照响应一维计算模型,该模型包含电缆屏蔽层和介质层间隙、介质层瞬态辐射感应电导率等计算模型,模拟了带状电缆直流和脉冲X射线辐照电流响应。模拟结果表明,在X射线注量相同的条件下,电缆直流和方波脉冲X射线响应具有类似的波形特征及相同的间隙电压。因此,在该计算模型描述的电缆X射线辐照响应机制下,可利用直流X射线开展相应的脉冲X射线辐照响应机制模拟。     

Effects of M 23C6 on the High-Temperature Performance of Ni-Based Welding Material NiCrFe-7

The effects of M ₂₃C₆ (M = Cr, Fe) on the high-temperature performance of the NiCrFe-7 welding rods and weld metals were studied by high-temperature tensile tests and microstructure analysis. M ₂₃C₆ at the grain boundaries (GBs) has a cube-on-cube coherence with one grain in the NiCrFe-7 weld metals, and the adjacent M ₂₃C₆ has the coherence relationship with the same grain. The grain with a coherent M ₂₃C₆ has a Cr-depletion region. The number and size of M ₂₃C₆ particles can be adjusted by heat treatment and alloying. There are two temperatures [T _E1: 923 K to 1083 K (650 °C to 810 °C) and T _E2: 1143 K to 1203 K (870 °C to 930 °C)] at which the GBs and grains of the NiCrFe-7 welding rod have equal strength during the high-temperature tensile test. When the temperatures are between T _E1 and T _E2, the strength of the GBs is lower than that of the grains, and the tensile fractures are intergranular. When the temperatures are below T _E1 or over T _E2, the strength of the GBs is higher than that of the grains, and the tensile fractures are dimples. M ₂₃C₆ precipitates at the GBs, which deteriorates the ductility of the welding rods at temperature between T _E1 and T _E2. M ₂₃C₆ aggravates ductility-dip-cracking (DDC) in the weld metals. The addition of Nb and Ti can form MX (M = Ti, Nb, X = C, N), fix C in grain, decrease the initial precipitation temperature of M ₂₃C₆, and mitigate the precipitation of M ₂₃C₆, which is helpful for minimizing DDC in the weld.     

卷取机恒张力控制方法与应用

本文通过分析卷取机负载的机械特性和变频电机的调速特性,对恒张力卷取的控制方法进行了论述,介绍了冷轧生产线中不同情况下卷取功率的计算方法。结合实例,给出了运用最大力矩控制法,合理选择卷取机的传动电机功率与减速比的公式,该计算结果和计算方法已得到实际验证。