基于FPGA的质谱仪高压脉冲电源设计

传统的高压脉冲电源产生的波形不易控制,脉冲幅值、频率、占空比等难以实时调节,而且脉冲的上升沿时间较长,无法满足飞行时间质谱仪（TOFMS）的苛刻要求。为解决上述问题,本文提出了一种用于飞行时间质谱仪的高压脉冲电源。该高压脉冲电源采用现场可编程门阵列（FPGA）做为主要芯片,产生PWM信号,经驱动电路和隔离电路后加在高速MOSFET开关管上。同时FPGA通过模拟串口和单片机或上位机通信,实现脉冲幅值、频率、延时、脉宽、脉冲个数等的实时调节。实际应用测试表明,该高压脉冲电源满足设计指标要求。     

Densification and anticorrosion performances of vacuum evaporated aluminium coatings on NdFeB magnets

Al coated NdFeB magnets obtained by vacuum evaporation technique were densified by high energy ball milling method.The surface morphology,metal composition and micro structure of the coatings were characterized by scanning electron microscopy,X-ray diffraction and X-ray photoelectron spectroscopy,respectively.The anticorrosive properties were investigated by potentiodynamic polarization curves and neutral salt spray test.The pores in the Al coatings of columnar crystals(Al) induced by the evaporation technique,were apparently filled in the following ball milling process,leading to the densification of Al coatings and the evident improvement of the anticorrosive performances.When treated with ball milling for 30 min,the sample achieves the best anticorrosive performances with the self-corrosion potential of-0.87 V,self-corrosion current density of 1.65 μA/cm~2 and the neutral salt spray(NSS) time of 144 h(red rust).The improvement of the anticorro sive performances of vacuum evaporated Al coating mainly lies in the densification effect of the coating,which depends on different loading conditions of ball milling process.     

Hydrated Bi-Ti-Bimetal Ethylene Glycol: A New High-Capacity and Stable Anode Material for Potassium-Ion Batteries

Potassium-ion batteries have emerged not only as low-cost alternatives to lithium-ion batteries, but also as high-voltage energy storage systems. However, their development is still encumbered by the scarcity of high-performance electrode materials that can endure successive potassium-ion uptake. Herein, a hydrated Bi-Ti bimetallic ethylene glycol (H-Bi-Ti-EG) compound is reported as a new high-capacity and stable anode material for potassium storage. H-Bi-Ti-EG possesses a long-range disordered layered framework, which helps to facilitate electrolyte ingress into the entire Bi nanoparticles. A suite of spectroscopic analyses reveals the in situ formation Bi nanoparticles within the organic polymer matrix, which can alleviate stresses caused by the huge volume expansion/contraction during deep cycles, thereby maintaining the superior structural integrity of H-Bi-Ti-EG organic anode. As expected, H-Bi-Ti-EG anode exhibits a high capacity and superior long-term cycling stability. Importantly for potassium storage, it can be cycled at current densities of 0.1, 0.5, 1, and 2 Ag⁻¹ for 800, 700, 1000, and even 6000 cycles, retaining charging capacities of 361, 206, 185, and 85.8 mAh g⁻¹, respectively. The scalable synthetic method along with the outstanding electrochemical performance of hydrated Bi-Ti-EG, which is superior to other reported Bi-based anode materials, places it as a promising anode material for high-performance potassium storage.     

“煤地质学”课程中提高学生科学素养的探讨

该文以煤地质学课程为例分析培养学生科学素养的过程。在理论课堂教学中注重培养学生不断探索的习惯,在实验教学中使学生树立正确的科学态度和人生价值观,在实践教学中让学生体验到自身的价值,使理论知识与实践生产紧密结合在一起。培养具有科学素养的大学生,是煤田地质领域需要大批综合素质人才的需要。     

热活化型水性聚氨酯贴合料的制备

研究了软硬段分子链结构、硬段含量、n(NCO)/n(OH)摩尔比和DMPA含量等,对水性聚氨酯(WPU)贴合料的活化温度和剥离强度影响。以结晶性较好的聚酯二元醇PBA-3000为起始原料,在摩尔比n(HDI)/n(IPDI)=7/3、n(NCO)/n(OH)=1.3和DMPA=4%的条件下,制得活化温度为50℃的热活化型WPU。应用结果表明:制得的热活化型WPU贴合料可用于热压延PVC革生产线,上料量为70g/m2时,PVC与涤纶基布的剥离强度达到35N/25mm,室温泡水24h后为32N/25mm。     

Low ohmic contact AIN/GaN HEMTs grown by MOCVD

AlN/GaN high-electron-mobility transistors （HEMTs） on SiC substrates were fabricated by metalorganic chemical vapor deposition （MOCVD） and then characterized. An Si/Ti/Al/Ni/Au stack was used to reduce ohmic contact resistance （0.33 g2.mm） at a low annealing temperature. The fabricated devices exhibited a maximum drain current density of 1.07 A/mm （Vows = I V） and a maximum peak extrinsic transconductance of 340 mS/mm. The off-state breakdown voltage of the device was 64 V with a gate-drain distance of 1.9 μm. The current gain extrinsic cutoff frequency fT and the maximum oscillation frequency fmax were 36 and 80 GHz with a 0.25 μm gate length, respectively.     

Balancing mechanical properties and processability for devulcanized ground tire rubber using industrially sized single‐screw extruder

Devulcanized ground tire rubber (DGTR) samples were produced using an independently developed industrially sized single‐screw extruder. The DGTR was further revulcanized to produce revulcanized DGTR (RDGTR) samples. The structure and properties of the produced samples were investigated via tests and characterization of sol fraction, crosslink density, Fourier transform infrared spectroscopy spectra, X‐ray photoelectron spectroscopy spectra, Mooney viscosity, curing characteristics, dynamic rheology, tensile properties, and surface morphology. The results demonstrate that the extruder can effectively break up crosslinked structure of ground tire rubber to achieve high devulcanization level (characterized by sol fraction and crosslink density), which is mainly associated with its moderate shear strength. The balance between mechanical properties and processability for the DGTR samples was analyzed. Lower ratios of main‐chain to crosslink scission and good processability (mainly characterized by modest Mooney viscosity) for the DGTR samples, and high tensile strengths and elongations at break for the RDGTR samples are obtained via appropriately combining the barrel temperature and screw speed. High quality DGTR sample with tensile strength and elongations at break of up to 11 MPa and 370%, respectively, is prepared under the conditions used in this work. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43761.     

运动模糊情况下障碍物检测预处理

针对在非结构化环境下,摄像机和拍摄目标相对运动造成的图像模糊情况,进行障碍物检测预处理。利用边缘锐度法判定获得的图像是否为运动模糊图像,如果是则利用傅里叶频谱和Radon变换得到点扩展函数后,利用 Lucy-Richardson法进行复原;为了降低后期障碍物检测的处理复杂度,利用提出的一种改进二维熵分割算法进行障碍物粗定位,面积阈值消除噪声影响,完成障碍物检测预处理。通过仿真实验验证了该方法的可行性和有效性,为智能汽车在非结构化环境下避障提供参考依据,为障碍物识别奠定基础。     

Catalase (CAT) Gene Family in Rapeseed (Brassica napus L.): Genome-Wide Analysis,Identification, and Expression Pattern in Response to Multiple Hormones and Abiotic Stress Conditions

Catalase (CAT) is an antioxidant enzyme expressed by the CAT gene family and exists in almost all aerobic organisms. Environmental stresses induce the generation of reactive oxygen species (ROS) that eventually hinder plant growth and development. The CAT enzyme translates the hydrogen peroxide (H₂O₂) to water (H₂O) and reduce the ROS levels to shelter the cells’ death. So far, the CAT gene family has not been reported in rapeseed (Brassica napus L.). Therefore, a genome-wide comprehensive analysis was conducted to classify the CAT genes in the rapeseed genome. The current study identified 14 BnCAT genes in the rapeseed genome. Based on phylogenetic and synteny analysis, the BnCATs belong to four groups (Groups I–IV). A gene structure and conserved motif analysis showed that Group I, Group II, and Group IV possess almost the same intron/exon pattern, and an equal number of motifs, while Group III contains diverse structures and contain 15 motifs. By analyzing the cis-elements in the promoters, we identified five hormone-correlated responsive elements and four stress-related responsive elements. Further, six putative bna-miRNAs were also identified, targeting three genes (BnCAT4, BnCAT6, and BnCAT8). Gene ontology (GO) enrichment analysis showed that the BnCAT genes were largely related to cellular organelles, ROS response, stimulus response, stress response, and antioxidant enzymes. Almost 10 BnCAT genes showed higher expression levels in different tissues, i.e., root, leaf, stem, and silique. The expression analysis showed that BnCAT1–BnCAT3 and BnCAT11–BnCAT13 were significantly upregulated by cold, salinity, abscisic acid (ABA), and gibberellic acid (GA) treatment, but not by drought and methyl jasmonate (MeJA). Notably, most of the genes were upregulated by waterlogging stress, except BnCAT6, BnCAT9, and BnCAT10. Our results opened new windows for future investigations and provided insights into the CAT family genes in rapeseed.