Investigation of nonvolatile holographic storage in LiNbO3:Mn:Ce:Fe crystal

We investigate the persistent holographic recording in triply doped LiNbO₃:Mn:Ce:Fe crystals at different oxidation/reduction states. The experimental results show that there is an optimum oxidation/reduction state, which results in the best dynamic range M/#. Compared with doubly doped LiNbO₃:Ce:Fe, we found that the nonvolatile diffraction efficiency and the best dynamic range M/# obtained in triply doped samples are larger than that obtained in doubly doped samples. The reason for the increase of the crystal about the nonvolatile diffraction efficiency and the dynamic range M/# was also explained.     

The analysis of spatial light to Bragg fiber coupling ratio

On the basis of the electromagnetic field mode matching theory, the coupling efficiency ratio from spatial light to Bragg fiber is analyzed, which shows that the coupling efficiency ratio is related to the radius of focused facular, the core radius of Bragg fiber and wave number of the core. By optimizing the value of such parameters appropriately, the Bragg fiber coupling efficiency ratio can be improved. It is also important for the analysis of the coupling efficiency of Bragg fiber, which can be applied to the free optical communication system and laser radar system.     

Dynamics of an intra-host model of malaria with a constant drug efficiency

In this paper, we investigate the dynamics of an intra-host model of malaria with logistic red blood growth, treatment and immune response. We provide a theoretical study of the model. We derive the basic reproduction number $\mathcal R_f$ which determines the extinction and the persistence of malaria within the body of a host. We compute equilibria and study their stability. More precisely, we show that there exists a threshold parameter $\zeta$ such that if $\mathcal R_f\leq\zeta\leq1$, the disease-free equilibrium is globally asymptotically stable. However, if $\mathcal R_f>1$, there exist two malaria infection equilibria which are locally asymptotically stable: one malaria infection equilibrium without immune response and one malaria infection equilibrium with immune response. The sensitivity analysis of the model has been performed in order to determine the impact of related parameters on outbreak severity. The theory is supported by numerical simulations. We also derive a spatio-temporal model, using Diffusion-Reaction equations to model parasites dispersal. Finally, we provide numerical simulations for parasites spreading, and test different treatment scenarios.     

Cournot competition with hyperbolic learning and myopic firms: A note

In this note, we provide a Cournot oligopoly model of learning-by-doing that incorporates both learning spillovers and organizational forgetting, relaxing the commonly made assumption of linear learning by considering a hyperbolic learning curve that depends on both own and rivals’ experience. The analysis is conducted under the assumption of myopic firms. We show that conditions exist under which more competition, captured by an increase in the number of firms, worsens both productive and allocative efficiency at the steady-state equilibrium.     

基于随机占优的股指期货市场有效性分析

2015年中金所出台严格监管措施后,股指期货成交低迷,异象频出。为验证严格监管措施对股指期货市场有效性的影响,本文利用随机占优DD测试法,为风险规避者和风险寻求者分别构建升序和降序占优模型。传统DD测试法用等间距划分的方式产生网格,且假设检验的两个判定阈值为相反数,这不符合金融数据的分布规律。因此,本文提出了对DD测试法的两处改进,利用“等频率划分法”产生网格,利用“非对称分位数法”产生阈值。实证方面,本文对三个股指期货及其现货的15分钟数据进行分析,发现在自股灾以来,上证50指数一阶占优于上证50股指期货,形成套利机会,且该套利策略的年化收益率、夏普比率和卡玛比率都非常优异。实证进一步显示,严格监管措施后占优数量达到最高峰,严格监管措施导致的股指期货功能受损比股灾更严重,而这一现象在中金所逐步放松监管措施后得以稍微缓解但没有根本改变。     

一种面向效率的系统多序参量识别方法

针对社会组织系统演化过程中效率性要求,基于系统演化有效性识别及评估,提出能够反映系统演化过程效率的多序参量识别方法,为提升系统演化过程效率提供可操作的技术参考。通过产出/投入视角分析多序参量形成过程,结合其对系统演化过程的影响,给出基于产出/投入的系统演化过程中多序参量效率原理;应用改进的数据包络分析方法和已有指标体系,建立面向效率的系统演化过程多序参量识别模型。最后,通过算例验证方法的科学有效性。     

基于氮化镓器件的LLC谐振变换器的驱动波形优化及损耗分析

随着第三代半导体器件氮化镓器件的逐渐成熟,使进一步提高直流电-直流电(DC-DC)变换器效率成为可能。探讨了氮化镓栅极正向阈值电压较小和具有反向导通能力的特性,并针对这些特性设计了新的驱动方式。之后从变换器损耗的角度,提出了基于损耗分析的最小损耗时的死区时间,确定了驱动波形的具体参数。并优化设计了主要磁性元件的设计流程以减小涡流损耗。经过仿真软件验证结论后最终给出了设计参数,并制作出了高效率的试验样机,证明了使用新型驱动电路的氮化镓LLC变换器高效、工作稳定。     

化学就地生热提高注蒸汽井井底干度可行性分析

蒸汽吞吐开采技术在国内外均有广泛应用,但工艺中存在设备参数难以控制、蒸汽运输过程中热损失大和注蒸汽成本高等缺点,导致注入井底的蒸汽干度大大降低,传递到井底的热量波及面积小,驱油效果差。针对以上问题,依据硝酸钠,氯化铵和尿素在弱酸环境下反应放热的原理,提出一种井底增干剂。该增干剂不仅在井底放出热量,提升井底干度,而且反应产生的无污染气体还能作为驱动力辅助驱油。最后,将此方法应用在实例中,证明了该设计的可行性。     

O3/NaClO协同氧化－吸附处理雨水的试验研究

采用O_3/NaClO协同氧化_吸附法对校园屋面雨水处理进行了试验研究。考察了粉末活性炭投加量、吸附时间、搅拌速度以及初始pH对COD、氨氮、TP和浊度去除率的影响;并进行了吸附等温线及动力学模型拟合。试验结果表明:粉末活性炭的最佳投加量为50 mg/L,最佳吸附时间为60 min,最佳搅拌速度为200 r/min,最佳初始pH为7时COD,氨氮,TP和浊度的去除率分别达到了68.87%,81.90%,78.79%,78.50%。COD和氨氮的吸附等温线更符合Freundilch模型,TP吸附等温线更符合Langmuir模型,拟二级动力学模型能更好的描述粉末活性炭对雨水中COD,氨氮和TP的吸附过程,相关系数均接近于1。     

无碱二元复合体系驱油机理研究

依据毛管数理论,传统观点认为界面张力越低,采收率越高,因此超低界面张力一直是评价表面活性剂界面活性的重要指标。基于并联岩心物理模拟试验研究了界面张力与提高采收率的关系,发现非均质油藏条件下低界面张力体系采收率高于超低界面张力体系。通过室内试验研究驱油体系形成乳液状态及粒径分布规律,揭示采收率与乳液粒径之间的关系。研究认为,低界面张力体系形成的乳液液滴粒径与高渗透层喉道尺寸匹配,能够有效封堵高渗透层,迫使更多注入液转向进入低渗透层,在扩大波及体积的基础上提高洗油效率,因此低界面张力体系比超低界面张力体系具有更好驱油效果。