FTIR光谱法测量不同化肥的氨挥发

氨挥发是化肥损失的重要途径,同时加剧了温室气体排放和水体富营养化。限于技术和资金条件,国内外氨挥发研究主要使用静态闭路箱法、半开放法、间歇通气法、质量平衡法及风洞法。文章利用FTIR光谱法,基于HITRAN数据库采用非线性最小二乘拟合气体浓度反演算法,测量对比了不同化肥的氨挥发,并简单分析了原因。试验表明,FTIR分析技术用于化肥的氨挥发测量,是一种操作简单,分析效率高,能满足实时、连续、准确要求的测量技术,可以满足野外田间作业的需要。     

电动效应作用下微通道内粒子运动的数值模拟

本文采用有限体积法数值模拟了轴向方波电场和直流电场作用下,具有不同电泳淌度粒子的运动情况.结果表明,在半个方波电场周期内,具有不同电泳淌度的粒子在相同的时间内达到各自的稳定速度,周期变化的方波电场使微粒子在微通道内做往复的运动;在直流电场作用下,两个不同电泳淌度的粒子会在轴向方向上产生位移差.定义从溶液中分离粒子的最短距离与微通道高度的比值为分离效率,数值模拟结果表明,分离效率随横向电场强度和粒子电泳淌度的增加而减小.     

Phase-dependence of inversionless gain in a Doppler broadened open four-level system

The effect of the relative phase (?) between the probe and driving fields on the gain without inversion (GWI) in a Doppler broadened open quasi Λ-type four level atomic system with vacuum induced coherence (VIC) for both co- and counter-propagating probe and driving fields cases is studied. It is shown that: (1) GWI and the probe detuning region in which GWI exists are very sensitive to variation of the relative phase; when values of the other parameters keep unvarying, by adjusting value of ?, the largest GWI can be obtained. (2) The Doppler width (D) also has dramatically modulation role on the phase-dependent GWI. When value of D is smaller, the value of ? which corresponds to the largest value of GWI is about π, when value of D is large enough, it is about π/2. (3) GWI varies periodically with ? varying, the period is 2π, but the concrete variation rule is closely related to value of D. (4) In the co-propagating case we can obtain much larger GWI than that in the counter-propagating case.     

Stability in a general coupled laser array

For the first time we have presented a method to investigate the stability of quiescent state in a coupled laser array. By introducing tiny perturbation, stability of quiescent state can be known by investigating eigenvalues of coefficient matrix of the corresponding linear differential equations. Only when real parts of the eigenvalues were all negative or zero, the corresponding quiescent state is stable. Two tapes of coupled laser array with loop and linear topological structure were studied respectively. It was found that there were innumerable quiescent states and they could be divided into several types based on phase relation. Some types were stable and others were unstable. Topological structure affects the stability of quiescent state in a coupled laser array.     

长亚甲基链段改性固化剂的制备与性能

采用二官能度环氧树脂对己二胺进行改性,得到了含多段长亚甲基链段的柔性固化剂。利用红外光谱表征其基本结构。采用环氧树脂E-44与之进行固化,通过不同温度下固化时间对力学强度影响的分析,初步确定其最佳固化条件为80 ℃,6 h。通过热重分析检测不同固化比例下固化产物的热稳定性,并采用差示扫描量热法研究该固化剂的固化动力学参数、反应活性、最佳固化温度及时间。对其固化物拉伸剪切强度进行测试,测试结果表明：在固化比例为1:0.5时,在-196 ℃、室温、60 ℃下的拉伸剪切强度分别为16.84,14.73和13.52 MPa,基本满足实际应用的需求。     

Ramsey interaction with transverse decay

The Ramsey fringe contrast of a pulsed optically pumped cold atom clock is strongly affected by the transverse decay of the atomic sample. This letter calculates the Ramsey fringe with focus on transverse decay, and analyzes the Ramsey fringe contrast with different transverse decay rates. By fitting the experimental data, we obtain the transverse decay rate in a cold atom sample at an approximate value of 30.5 s1 , which is much smaller than that in a cell.     

Spinel lithium titanate (Li4Ti5O12) as novel anode material for room-temperature sodium-ion battery

This is the first time that a novel anode material, spinel Li₄Ti₅O₁₂ which is well known as a “zero-strain” anode material for lithium storage, has been introduced for sodium-ion battery. The Li₄Ti₅O₁₂ shows an average Na storage voltage of about 1.0 V and a reversible capacity of about 145 mAh/g, thereby making it a promising anode for sodium-ion battery. E_x-situ X-ray diffraction (XRD) is used to investigate the structure change in the Na insertion/deinsertion process. Based on this, a possible Na storage mechanism is proposed.     

基于低阶矩阵最大特征值的复杂网络牵制混沌同步

虽已对复杂网络牵制同步需要牵制结点数量及牵制结点数量与耦合强度的关系进行了研究,然而快速计算牵制结点数量仍是大规模复杂网络面临的一个重要问题.研究发现了复杂网络耦合矩阵主子阵最大值递减规律,由此提出了快速计算复杂网络牵制结点数量的方法,揭示了不同的牵制策略与牵制结点数量之间的关系.数值仿真显示了在无标度网络和小世界网络上三种不同的牵制策略下,牵制结点数与主子阵最大特征值的变化规律;最后给出了一个在无标度网络上采用随机选择结点策略的牵制同步实例.     

噪声诱导的二维复时空系统的同步研究

研究了一类噪声诱导的二维复时空系统的同步问题.首先讨论了二维复Ginzburg-Laudau(CGL) 方程随时间和空间变化的时空混沌特性;其次,研究了时空噪声驱动下CGL系统的同步问题.理论上利用线性稳定性分析,得到了常数激励下CGL系统达到稳定态的临界强度;结合噪声的随机性和非零均值特性, 揭示了噪声诱导同步的机理;并从理论上和数值上分别给出了达到同步所需要的控制参数和噪声强度满足的条件,实现了两个非耦合CGL系统的完全同步.结果表明,数值模拟和理论分析有很好的一致性.     

90°弯管内冰浆流动特性数值模拟

基于欧拉法建立了冰浆流动的混合模型,对冰浆在90°弯管内的流动特性进行了数值模拟研究,获得了弯管内冰浆的流场和冰晶颗粒的运动轨迹,探讨了弯管管径、曲率半径及冰浆的流速、浓度参数对弯管内冰浆压降的影响,并对弯管压降的模拟结果与实验结果进行对比,两者吻合较好。结果表明:在计算参数范围内,弯管压降随冰浆流速、浓度及弯管曲率半径的增大而增大,随弯管管径的增大而减小;冰浆在弯管内流动形成二次流现象,两个漩涡区域出现在弯管截面两侧;漩涡导致部分冰晶颗粒的运动轨迹发生改变,并使其向弯管下方的负压区聚集,增大了冰晶颗粒的碰撞几率。