海平面宇宙射线重粒子的质量谱及通量的测量

本文介绍了一个由飞行时间测量系统构成的实验装置,描述了这个实验装置的各个组成部分和它的性能,并给出了海平面宇宙射线重粒子的质量谱及通量的测量结果。     

談談怎样处理数学習題的問题

究竟怎样改进数学作業的檢查和批改工作,是一个爭論已久的問題,也是我个人很有兴趣的一个問題。我認为这一工作的改进要牽涉到下面三个問題:(1)怎样深入地鑽研教材,認真备課,积極地改进教学方法,使学生当堂弄会弄透,以达到融会贯通。     

Characteristics of Flow around an Impulsively Rotating Square Cylinder via LB-DF/FD Method

Flow around an impulsively rotating square cylinder in a viscous fluid in range of 1 ≤ Re ≤ 300 is numerically investigated by the previously developed LB-DF/FD method, which combines the lattilce Boltzmann method （LBM） and direct-forcing fictitious domain （DF/FD） scheme. Results show that in total three kinds of transient characteristics depending on Re are observed： 1 ≤ Re ≤ 20, four vortices arising from the corners of the square cylinder separate from the surfaces and gradually become stable without vortex integration or shedding; 20 ≤ Re 〈 100, vortices integration is observed when they grow long enough, then separated from each other; Re ≥ 100, vortex shedding takes place in this regime. The shedding vortex joins the downstream vortex to form a new one. It is also found that vortex shedding happens more than one time when Re ≥ 160. Furthermore, each vortex shedding induces a fluctuation in the torque exerted on the cylinder.     

旋转体系中湍流的LBM模拟

采用基于多松弛时间因子的格子Boltzmann方法对旋转体系中的湍流进行数值研究,考察Rossby数和Ekman数对湍流的影响,包括湍流能量及其耗散率、速度、涡结构及湍流的耗散尺度即Kolmorogov尺度和积分尺度等.研究表明,系统的旋转延缓了湍流能量的衰减速率,逐步破坏初始涡结构的均匀性,与旋转方向相反的涡逐步被抑制,并最终形成若干与旋转同向的涡柱.结果还表明,系统旋转越快,湍流的耗散尺度越小而积分尺度越大.     

利用海洋环境噪声直接提取海底反射系数

提出了一种利用海洋环境噪声直接(非迭代)提取海底反射系数的方法,基于海洋环境噪声垂直相关函数与方向密度函数的相似性,结合海洋环境噪声射线理论,由两个垂直排列的水听器实现海底反射系数的被动获取.方法适应性的仿真分析说明较高海况下且近场无航船干扰的海洋环境噪声数据有利于方法的实现;对于两层海底,海洋环境噪声垂直相干函数经高...     

液体物性对雾化射流液雾粒径的影响

对不同液体在空气中湍动雾化射流的气液两相流场进行了数值模拟.建立了一次雾化的一维模型,分析了粘度、表面张力和气液质量流量比对液雾粒径的影响趋势,采用基于粒子追踪法的二次雾化三维模型,分析了物性和各种工况对液雾粒径沿轴向分布的影响程度.计算结果和已公开发表的实验数据进行比对,得到了较好的吻合,在此基础上,分析了影响气泡雾化喷嘴雾化质量的主要因素.     

Synthesis of flower-like WS2 by chemical vapor deposition

Flower-like tungsten disulfide (WS₂) with a diameter of 5-10 μm is prepared by chemical vapor deposition (CVD). Scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), Raman spectroscopy, and ultraviolet-visible (UV-vis) spectroscopy are used to characterize its morphological and optical properties, and its growth mechanism is discussed. The key factors for the formation of flower-like WS₂ are determined. Firstly, the cooling process causes the generation of nucleation dislocations, and then the "leaf" growth of flower-like WS₂ is achieved by increasing the temperature.     

Large-scale absolute distance measurement with dual free-running all-polarization-maintaining femtosecond fiber lasers

We demonstrate a robust femtosecond LIDAR setup by using two free-running environmentally stable allpolarization-maintaining nonlinear amplified loop mirror mode-locked fiber lasers. Based on the asynchronous optical sampling method, a ranging accuracy of ±2 μm within 65 m has been achieved, as tested in an 80-m-long underground optical tunnel. Through the Kalman filter in real-time data processing, the measurement accuracy can be maintained at a 200 Hz update rate. This setup provides a practical tool for various large-scale industrial and astronomical ranging applications.     

温敏核不育系水稻株1S及其矮秆突变体SV14茎的蛋白质组学比较

采用双向凝胶电泳对温敏核不育水稻株1S和其矮秆突变体SV14的茎(穗颈下第1节和第2节)蛋白进行了分离, 通过银染显色, 获得了分辨率和重复性较好的双向电泳图谱. 选取了26个蛋白质点采用MALDI-TOF-MS进行肽质谱指纹图分析, 最终有12个蛋白质点得到了可靠鉴定. 其中在SV14中相对于株1S上调的仅有OSJNBa0039C07.13 蛋白, 其它蛋白均表现为下调. 这些差异蛋白按照功能可分为4类: (1) 能量代谢相关蛋白; (2) 次生代谢相关蛋白; (3) 调控蛋白; (4) 未知蛋白. 对光合系统Ⅱ氧延伸复合物蛋白质前体2, 果糖二磷酸醛缩酶, UDP-葡糖醛酸脱羧酶对应的基因进行了半定量RT-PCR分析, 发现这几个基因与蛋白质的表达不一致, 可能是RNA发生了翻译后修饰而减少了蛋白表达量的结果. 这些差异蛋白很可能与水稻矮化有关, 为水稻矮秆基因的寻找提供了另一个有效途径.     

发光颜色可调的白磷钙矿结构Ca8MgBi(PO4)7∶Ce3+，Tb3+荧光粉的制备、发光性能及能量传递

采用具有白磷钙矿结构的磷酸盐作为目标产物,通过高温固相法制备了发光颜色可调的Ca₈MgBi(PO₄)₇∶Ce³⁺,Tb³⁺荧光粉。利用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)和荧光光谱等表征手段对其物相组成、微观形貌及发光性能进行了详细研究。结果表明：掺杂少量的Ce³⁺、Tb³⁺并没有改变Ca₈MgBi(PO₄)₇基质的晶体结构。荧光光谱和荧光寿命曲线确定了Ce³⁺-Tb³⁺之间存在能量传递,其能量传递机制为四极-四极相互作用,能量传递效率可达81%。固定Ce³⁺浓度而逐渐增加Tb³⁺的掺杂量时,系列Ca₈MgBi(PO₄)₇∶0.08Ce³⁺,yTb³⁺荧光粉的发...