Ni2+含量对纳米Ni-Zn铁氧体电磁损耗特性的影响

以聚乙二醇为表面活性剂辅助水热法制备了纳米NixZn1-xFe2O4(x=0.4、0.5、0.6、0.7)铁氧体,通过XRD、FESEM、TEM和PNA分析,研究了不同的Ni2+含量对Ni-Zn铁氧体的粒度、形貌及其电磁损耗特性的影响.结果表明,水热法制备的晶体具有良好的结晶度,Ni2+含量不会影响样品的形态和结构,样品颗粒呈类球形,粒径在20～30 nm,在1～ 18 GHz的测试条件下具有介电损耗与磁损耗.Ni-Zn铁氧体电磁损耗随Ni2+含量的增加先增大后减小,当Ni2+含量x=0.6时,晶体晶化更加完整,粒度更加细化,对小于14 GHz中低频微波电磁损耗能力更强,在3GHz处,磁滞损耗正切tanδm达到最大值为1.03,介电损耗正切tanδe在3 GHz、9.5 GHz分别达到0.052、0.057,具有一定的微波吸收能力.     

基于江西地区多卫星数据的气溶胶立体分布研究

利用长时间序列（2007~2014年）的MODIS/Terra数据探讨了江西地区气溶胶光学厚度（aerosol optical depth, AOD）空间变化特征,发现该地区平均AOD呈现由南往北逐渐递增的趋势,其中,九江和南昌达到最高。同时,利用CALIPSO/CALIOP 垂直特征掩膜获得了气溶胶层与云层的混合和分离状态,计算了气溶胶、不同子类型气溶胶和云的垂直概率分布和最大似然高度（maximum probability height, MPH）。结果表明：气溶胶主要聚集在1~3.5 km,气溶胶层和云层混合状态出现的概率高于分离状态。在2～4 km之间,春季污染沙尘出现的概率最高,冬季次之,夏季与秋季相当,而烟尘气溶胶夏季出现的概率最高,春、冬季相当,秋季次之。基于夜间CALIOP数据计算得到的气溶胶和云的MPH均表现出较大的季节差异性。     

基于MEMS压阻传感器的低功耗高过载测试系统设计

为了检验弹体在高冲击环境下的工作情况,提出了一种基于压阻传感器的高过载、低功耗的测试系统设计方案。该系统可承受2×105g的过载冲击测试,且具有采样率高、体积小、功耗低的特点。通过打靶实验验证:在过载测试过程中该系统具有承受高冲击的能力,并能精确地采集到信号微弱变化,保证了弹体在飞行中记录数据的准确性。     

Carrier transport in III–V quantum-dot structures for solar cells or photodetectors

According to the well-established light-to-electricity conversion theory,resonant excited carriers in the quantum dots will relax to the ground states and cannot escape from the quantum dots to form photocurrent,which have been observed in quantum dots without a p–n junction at an external bias.Here,we experimentally observed more than 88% of the resonantly excited photo carriers escaping from In As quantum dots embedded in a short-circuited p–n junction to form photocurrent.The phenomenon cannot be explained by thermionic emission,tunneling process,and intermediate-band theories.A new mechanism is suggested that the photo carriers escape directly from the quantum dots to form photocurrent rather than relax to the ground state of quantum dots induced by a p–n junction.The finding is important for understanding the low-dimensional semiconductor physics and applications in solar cells and photodiode detectors.     

Effects of multiple interruptions with trimethylindium-treatment in the InGaN/GaN quantum well on green light emitting diodes

In this study, the influence of multiple interruptions with trimethylindium(TMIn)-treatment in InGaN/GaN multiple quantum wells(MQWs) on green light-emitting diode(LED) is investigated. A comparison of conventional LEDs with the one fabricated with our method shows that the latter has better optical properties. Photoluminescence(PL) full-width at half maximum(FWHM) is reduced, light output power is much higher and the blue shift of electroluminescence(EL) dominant wavelength becomes smaller with current increasing. These improvements should be attributed to the reduced interface roughness of MQW and more uniformity of indium distribution in MQWs by the interruptions with TMIn-treatment.     

Large single crystal diamond grown in FeNiMnCo-S-C system under high pressure and high temperature conditions

Large diamonds have successfully been synthesized from FeNiMnCo-S-C system at temperatures of 1255-1393 ℃and pressures of 5.3-5.5 GPa.Because of the presence of sulfur additive,the morphology and color of the large diamond crystals change obviously.The content and shape of inclusions change with increasing sulfur additive.It is found that the pressure and temperature conditions required for the synthesis decrease to some extent with the increase of S additive,which results in left down of the V-shape region.The Raman spectra show that the introduction of additive sulfur reduces the quality of the large diamond crystals.The x-ray photoelectron spectroscopy(XPS) spectra show the presence of S in the diamonds.Furthermore,the electrical properties of the large diamond crystals are tested by a four-point probe and the Hall effect method.When sulfur in the cell of diamond is up to 4.0 wt.%,the resistance of the diamond is 9.628×10~5 Ω·cm.It is shown that the large single crystal samples are n type semiconductors.This work is helpful for the further research and application of sulfur-doped semiconductor large diamond.     

网络结构、采纳者偏好与创新扩散:基于采纳者决策过程的创新扩散系统动力学模型仿真分析

在对采纳者决策过程分析的基础上,将网络结构和采纳者偏好作为核心参数,构建基于采纳者决策过程的创新扩散系统动力学模型。对模型进行仿真发现,在采纳者趋同化偏好条件下,网络平均度、网络重连概率与采纳者偏好强度的变动趋势与创新扩散效率的变动趋势相同,而在采纳者差异化偏好条件下则与创新扩散效率变动趋势相反。网络平均路径长度对创新扩散的影响方向与采纳者偏好特征无关,提高网络平均路径长度会始终降低创新扩散的效率。采纳者的趋同化偏好能够放大创新扩散对网络结构变量与采纳者偏好强度变量的敏感程度,采纳者差异化偏好则会缩小创新扩散对网络结构变量与采纳者偏好强度变量的敏感程度。研究结果对于制定创新推广策略具有一定的指导意义。     

Coexistence of unipolar and bipolar modes in Ag/ZnO/Pt resistive switching memory with oxygen-vacancy and metal-Ag filaments

In this study, the unipolar resistive switching(URS) and bipolar resistive switching(BRS) are demonstrated to be coexistent in the Ag/Zn O/Pt memory device, and both modes are observed to strongly depend on the polarity of forming voltage. The mechanisms of the URS and BRS behaviors could be attributed to the electric-field-induced migration of oxygen vacancies(VO) and metal-Ag conducting filaments(CFs) respectively, which are confirmed by investigating the temperature dependences of low resistance states in both modes. Furthermore, we compare the resistive switching(RS)characteristics(e.g., forming and switching voltages, reset current and resistance states) between these two modes based on VO- and Ag-CFs. The BRS mode shows better switching uniformity and lower power than the URS mode. Both of these modes exhibit good RS performances, including good retention, reliable cycling and high-speed switching. The result indicates that the coexistence of URS and BRS behaviors in a single device has great potential applications in future nonvolatile multi-level memory.     

基于分形理论的不同草原可燃物及裸土野外光谱识别研究

草原火灾一直是影响我国草原生态系统的重要因素,对其展开研究具有重要的现实意义。遥感技术的发展,为草原火灾的相关研究提供了详尽准确的数据,节省了大量的人力物力和财力。但在实际应用中,如何识别不同可燃物及裸土一直是难点问题。试图将分形理论应用到枯草及裸土的光谱识别研究中,为上述问题寻找新的研究思路和方法。该研究运用美国ASD公司的FS3地物光谱仪对吉林省长岭县西部草场的优势种羊草(Leymuschinensis)、芦苇(Reed)、虎尾草(Chlorisvirgata)、全叶马兰(Kalimerisintegrifolia)、蒙古蒿(Artemisia mongolica)的枯萎植株及裸土进行了野外光谱测量。并利用Matlab工具,对上述研究对象的平均野外反射光谱曲线进行了包络线提取和分形盒维数的计算。经过光谱分析,裸土和虎尾草的野外光谱反射强,羊草、芦苇和蒙古蒿的野外光谱反射相对较弱,但彼此的谱型较为相近,较难识别区分。而全叶马兰的平均野外光谱反射强,且谱型与其他研究对象有较大差异,可以很好的识别。通过分形分析,研究对象的平均野外反射光谱曲线与包络线具有典型的分形特征。以分维数作为分类指标,对研究对象进行聚类分析,完成了不同地物的野外光谱识别。该方法与传统光谱分析的方法相比,能够更好地利用数学方法,客观的通过识别参数对目标进行识别,为今后进行其他种类枯草的识别和提取研究提供了新的思路和方法。     

景区游憩价值评估的ZTCIA模型及其普陀山实证研究

景区游憩价值的评估可为景区可持续发展提供参考. 对游憩价值评估方法中旅行费用法的发展、存在问题和模型进行了阐述, 总结了国内外旅行费用法研究的不足之处, 并结合旅行费用法传统模型(ITCM和ZTCM)和旅行费用区间模型(TCIA)提出区域旅行费用区间分析(ZTCIA)模型. 为验证改进模型的实用性, 运用ZTCIA和ITCM模型评估了普陀山游憩价值, 2种模型的评估值分别为134.75亿元与135.95亿元, 从评估步骤上看, 2种模型存在一定的互补性, 因此, 最终将平均值135.35亿元作为普陀山2014年的游憩价值.