Rheological phase reaction synthesis and electrochemical performance of LiFe2/3Mn1/3PO4/C cathode for lithium-ion batteries

LiFe_2/3Mn_1/3PO₄/C composite was prepared by the rheological phase reaction using LiH₂PO₄, Li₂CO₃, FePO₄, Mn(Ac)₂·4H₂O and ascorbic acid as starting materials. The crystal structure and morphology of as-synthesized sample were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The analysis of XRD results showed that the obtained sample was single-phase with orthorhombic olivine-type structure (Pnma space group). SEM micrographs revealed that the sample was aggregates, with an irregular morphology. The initial discharge capacity was 166.9, 149.1, 139.6, 112.8, 82.93 mAh g^??1 at the rate of 0.1, 0.5, 1, 2, and 10 C, respectively. And when the rate was 0.1, 0.5, 1, 2, and 10 C, the capacity retention was 92.2%, 90%, 92.9%, 97.6%, 91.5% after 50, 100, 200, 200, 500 cycles, respectively.

     

基于弧长参数空间的汽车车身表面网格生成

提出了基于弧长参数空间的表面网格生成方法，即引入原始的CAD数据模型，通过弧长参数化将其正映射至参数空间，按照计算要求优化网格品质，再逆映射回物理空间，在映射的同时保留表面几何特征，以达到不改变曲面特征形状的目的。将其应用于汽车车身表面网格的生成，并取得了很好的效果。该方法为具有复杂几何外形的物体表面网格的生成提供了一个便利的途径，也为进一步生成三维空间网格奠定了基础。     

3003铝合金蠕变行为与本构方程

研究了3003铝合金冷轧变形后再结晶组织控制和175~250℃、外加应力25~50 MPa条件下3003铝合金的蠕变行为。采用弹性模量归一化应力幂律蠕变本构方程,对实验数据进行线性拟合,建立了能够较好描述稳态蠕变速率与应力、温度三者之间关系的本构方程。结果表明:采用350℃和600℃的两步再结晶退火,可获得有利于提高合金蠕变性能的长条状再结晶组织;温度越高,应力增加对稳态蠕变速率增加的贡献越大;不同温度下3003铝合金的蠕变机制不同,175℃时,应力指数n=3.5,蠕变主要由位错滑移控制;在200~250℃范围内,n处于5.1~8.6之间,蠕变主要由位错攀移控制。     

3D‐printed high‐gain circularly polarized antenna for broadband millimeter‐wave communications over the power line

It is well known that high transmission loss occurs when millimeter waves traveling through the atmosphere. As an alternative, power line is proposed as a transmission media to combat the high loss. In this article, a three‐dimensional (3D) printed high‐gain circularly polarized antenna was proposed for millimeter‐wave broadband power line communications. It has a simple structure, where tapered slots are designed between the upper and lower layers of the waveguide to generate the circularly polarized operation. A wide impedance bandwidth of 31.58% (24‐33 GHz) and an axial ratio bandwidth of 28.07% (24.5‐32.5 GHz) are achieved by the proposed design. A maximum gain of 11.2 dBi is measured from the 3D printed structure. The proposed antenna has a simple structure which is easy to adjust to any working frequency. The antenna can be excited by properly integrated to the waveguide that connected to the power line end. The use of 3D printing technology enables a low‐cost solution millimeter‐wave broadband communications over the power line.     

单层窗户玻璃贴太阳控制膜的节能性研究

分析了单层窗户玻璃贴太阳控制膜的节能原理,比较了贴太阳控制膜与不贴太阳控制膜玻璃的热工性能。实验测试了单层窗户玻璃贴太阳控制膜与不贴太阳控制膜的酒店房间集中空调系统的能耗及室内照度,结果表明贴太阳控制膜有一定的节能效果。理论分析计算了集中空调系统能耗差,实验结果与理论计算结果基本吻合。     

Colorimetric determination of melamine by pyridine-3-boronic acid modified gold nanoparticles

A rapid, simple and sensitive colorimetric detection method for melamine was proposed based on pyridine-3-boronic acid (PBA) modified gold nanoparticles (AuNPs). The formation of supramolecular hydrogen-bonded structure between PBA and melamine resulted in the aggregation of PBA modified AuNPs and the color change from red to blue. Melamine could be detected by colorimetric response of AuNPs that could be detected by naked eyes or a UV-vis spectrophotometer. The detection concentration of melamine ranged from 6.0 x 10(-8) to 1.6 x 10(-6) M, and the detection limit (3sigma) was 3.0 x 10(-8) M (i.e., 3.2 ppb). This provided an effective and facile colorimetric sensor for real-time and on-site determination of melamine. Particularly, the proposed method could be used to detect melamine in pretreated liquid milk products with high sensitivity and low interference, and the recoveries were from 95% to 102%.     

Electrochemical synthesis and characterization of a novel thiazole-based copolymer and its application in biosensor

A novel copolymer based on 2-aminothiazole (AT) and 2-amino-4-thiazoleacetic acid (ATA) is electrochemically synthesized and then characterized using UV–visible absorption spectroscopy (UV–vis), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and electrochemical techniques. The results confirmed that the obtained polymer was a copolymer rather than a blend or a composite of the respective homopolymers and could improve the electrochemical response of both positively and negatively charged analytes. Therefore, the copolythiazole film was applied to determine ascorbic acid (AA), dopamine (DA) and uric acid (UA). It is found that the peak separating degrees and peak currents of AA, DA and UA at copolythiazole modified electrode were much better than those at bare GCE. Under the optimum conditions, the linear calibration curves were obtained in the range of 10–2000 μM for AA, 1–150 μM for DA, 1–180 μM for UA. The detection limits of AA, DA and UA were 2, 0.04 and 0.4 μM, respectively (S/N = 3). The practical application of the modified electrode was demonstrated by the determination of UA in urine sample.     

亲水作用色谱-电喷雾串联质谱法测定水产品中的氟苯尼考胺的残留量

建立亲水作用色谱-电喷雾串联质谱测定水产品中氟苯尼考胺残留量的测定方法。样品用碱性乙酸乙酯提取,以正己烷和脂肪吸附材料去除油脂,用5 mmol/L乙酸铵溶液(含0.2%甲酸)和乙腈作为流动相,以梯度洗脱方式在Acquity UPLC BEH HILIC柱(55 mm×2.1 mm,1.7μm)色谱柱上分离,以电喷雾离子源正离子模式进行质谱分析,基质外标法定量。结果表明,氟苯尼考胺的质量浓度在0.1~20μg/L范围内呈良好的线性,相关系数(r2)大于0.990。在1.0~50.0μg/kg加标水平下,虾、黄鱼、鳗鱼、烤鳗的平均回收率为70.5%~87.7%,相对标准偏差为4.8%~11.6%,定量限为1.0μg/kg。该方法简单、灵敏、稳定,可满足水产品中氟苯尼考胺残留量的检测和确证需要。     

Simultaneous determination of 3,4-dihydroxyphenylacetic acid, uric acid and ascorbic acid by poly(L-arginine)/multi-walled carbon nanotubes composite film

The poly(L-Arginine)(PArg)-multiwalled carbon nanotubes (MWCNTs) composite film was used to modify glassy carbon electrode (GCE) to fabricate PArg/MWCNTs/GCE through electropolymerization of L-Arginine on MWCNTs/GCE. The PArg/MWCNTs/GCE exhibited high electro-catalytic activities towards the oxidation of 3,4-dihydroxyphenylacetic acid (DOPAC), uric acid (UA), and ascorbic acid (AA), and could be sensitively used for simultaneous determination of DOPAC, AA, and UA in pH 7.4 phosphate-buffered solution (PBS).The linear ranges were 7 microM to 2.7 mM for DOPAC, 3 microM to 1.2 mM for UA, and 70 microM to 1.4 mM for AA. The detection limits were 1.3 microM for DOPAC, 0.7 microM for UA and 20 microM for AA.     

竖直U型埋管地下换热器的传热模型

以钻孔壁为界,将所研究的传热区域划分为土壤部分和钻孔内两部分.对于钻孔外土壤部分的传热过程,采用线热源理论建立非稳态模型进行分析讨论;在钻孔内,对一维模型和二维模型进行了对比,从而得出增强地下换热器换热的措施.