“守恒法”在力学中的应用

通过具体的实例介绍了"守恒法"在力学中的应用.     

一类厄尔尼诺一南方涛动充电-放电振子模型研究

通过数学变换将一类厄尔尼诺．南方涛动（简称ENSO）的充电．放电振子模型转换成vanderPol方程,由vanderPol方程的定性分析严格证明了该ENSO振荡子模型存在一个稳定的极限环．     

基于节点重构的扩散方程有限体积格式

研究扭曲网格上扩散方程的九点格式.以经典的九点格式为基础,在通量连续条件下,构造出节点未知量一种新的计算方法,进而得到所希望的格式.分析及数值实验表明,在扭曲网格上,该格式对具有连续或间断扩散系数的问题能够保持较高的精度.     

医学院校非影像专业开设“医学影像物理原理”选修课程探索

编制了一套通俗易懂、能促进医学影像原理普及的基本上"立体化"的教材,主要由学习软件、模拟试验、纸质教材和网页形式的CAI课件构成.使医学院校在校学生、临床医务工作者能在较短的时间内掌握X-CT、MRI成像基本原理.     

Secondary Beam Fragments Produced by 200 and 400 MeV/u ^12C^6＋ Ions in Water

Based on the GEANT4 toolkit, we study the transportation of nucleons and nuclei in tissue-like media. The fragmentation of projectile nuclei and secondary interactions of produced nuclear fragments are considered. Livermore data is used to calculate electromagnetic interaction of primary and secondary charged particles. We validate the models using experimental data of 200 MeV/u and 400 MeV/u carbon ions, interacting with tissue equivalent materials of water. The model can well describe the depth-dose distributions in water and the doses measured for secondary fragments of certain charge and certain mass number. The secondary beam fragments produced by 200 MeV/u and 400 MeV/u ^12C^6＋ ions in water are investigated using the model. When the primary nuclei are in water, several neutron production mechanisms are involved. The light charged particles （p, d, t, ^3He and ^4He） and fast neutrons contribute to the dose tail behind the Bragg peak. The ^11C fragments which may be the most suitable nuclei for monitoring the energy deposition in carbon-ion therapy are also discussed.     

Study ao（980）-f0（980） mixing in charmonium decays

In this proceeding, we propose to directly measure the a0^0（980）-f0 （980） mixing in J/ψ→φf0（980）→φa0^0（980） and Xc1→π^0a0^0（980） →π^0f0（980） with the upgraded Beijing Electron Positron Collider（BEPCII） with BESIII detector. We show that a narrow peak of about 8 MeV will be produced by the a0^0（980）-f0（980） mixing, and the predominant feature makes it standing out from the background contributions. The predicted branching ratios for these two reactions are both expected to be about O（10^-6）, which is unambiguously accessible with 10^9 J/ψ and 3 × 10^8 Xc1 at BESⅢ.     

Structure and Luminescence of Carboxylic Acid Samarium and Europium Complexes

Two crystals, [Sm(Hcpna)(cpna)·3 H_2O]n(1) and [Eu(Hcpna)(cpna)·2 H_2O]n(2),have been synthesized by solvothermal method based on Sm3+ and Eu3+ with multiple acid ligands5-(4-carboxyphenoxy)nicotinic acid(H_2cpna), and the new complexes have been characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy, thermogravimetric analysis and fluorescence analysis. Complex 1 exhibits a 1 D chain structure. It crystallizes in the triclinic system, space group P1 with a = 5.9738(11), b = 12.528(2), c = 18.021(4) ?, α = 93.156(3)o, β =98.067(3)o, γ = 92.692(3)o, V = 1331.3(4) ?3, Z = 2, S = 1.069, F(000) = 702, R = 0.0277 and wR =0.0688(I 2σ(I)). Complex 2 shows a two-dimensional network structure, which crystallizes in monoclinic system, space group C2/c with a = 13.6733(19), b = 18.422(3), c = 10.4307(15) ?, β =93.881(2)o, V= 2621.4(7) ?3, Z = 4, S = 1.110, F(000) = 1372, R = 0.0302 and wR = 0.0811(I 2σ(I)). The solid-state fluorescent test results show tcomplex 1 has weaker fluorescence intensity than the ligand. However, complex 2 has excellent fluorescence properties, and can emit bright red light under the irradiation of ultraviolet lamp.     

基于可调控狭缝光子晶体波导的微粒操控

提出并设计了一种用于真空中操控亚波长微粒的可调控渐变狭缝光子晶体波导结构.该结构利用光力将微粒捕获到狭缝中,使其沿光传输方向传输,并通过外加折射率调控的方式,将微粒输运到所需位置.分析了狭缝光子晶体波导的带隙结构、传输特性与微粒的受力情况,计算了热调控光子晶体波导的功耗与温度分布.结果表明,利用狭缝宽度渐变的硅基光子晶体波导,通过热调控改变硅折射率,可以实现光波截止位置从出射端到入射端的移动;对于总长度18μm的狭缝光子晶体波导,从入射端到出射端狭缝缩窄4nm时,控制微粒位置所需的折射率变化为0.012,而改变折射率所需的加热功率不高于13.7mW.这一结构将为微粒操控提供一种可能的实现方案.     

连续碳纤维增强碳化硅的辐照效应

连续碳纤维增强碳化硅材料除了具有碳化硅材料固有的低中子活化性能,低衰变热性能和低氚渗透性能等优点以外,还具有密度低、线性膨胀系数小、高比强度、高比模量、耐高温、抗氧化、抗蠕变、抗热震、耐化学腐蚀、耐盐雾、优良的电磁波吸收特性等一系列优异性能,是各类核工程重要的潜在候选材料。在核聚变工程应用领域,连续碳纤维增强碳化硅材料作为第一壁材料不可避免地会受到各种辐射粒子的影响。研究清楚这些辐射粒子对它的辐照效应对其在核工程领域的安全使用至关重要。采用蒙特卡罗方法与分子动力学方法进行模拟计算,研究了氕、氘、氚和氦四种粒子对连续碳纤维增强碳化硅的辐照效应。SRIM和LAMMPS计算结果表明:当入射原子能量为100 eV,连续碳纤维增强碳化硅中碳的浓度在80%~85%时,氕、氘、氚和氦原子的溅射率存在最小值;入射粒子的种类对溅射率的影响显著,氦原子的溅射率大于氘原子和氚原子,而氘原子和氚原子的溅射率相差不大但均显著大于氕原子;溅射率随入射能量的增加先迅速增加后逐渐减小,氕、氘、氚和氦原子入射能量分别在200,400,600和800 eV时存在溅射率最大值;当氦原子入射能量为100 eV时,溅射率随入射角度的增加而逐渐减少。这些结果对连续碳纤维增强碳化硅材料在核工程上的应用具有一定的参考意义。Continuous carbon fiber reinforced silicon carbide material has the low neutron activation, low decay heat performance and tritium permeability, which are inherent performance of silicon carbide materials. It also has other advantages such as low density, small linear expansion coefficient, specific strength and specific modulus, high temperature resistance, oxidation resistance, creep resistance, thermal shock, resistance to chemical corrosion, salt fog resistance, excellent electromagnetic wave absorption properties, etc. It is an important potential candidate material in various field of nuclear engineering. In the field of nuclear fusion engineering applications, continuous carbon fiber reinforced silicon carbide as the first wall material will inevitably be bombarded by a variety of radiation particles. The radiation effect is critical to its safe use in nuclear engineering. The Monte Carlo method and the molecular dynamics method were used to study the radiation effect of protium, deuterium, tritium and helium on continuous carbon fiber reinforced silicon carbide. The SRIM and LAMMPS simulation results show that when the incident energy is 100 eV and the concentration of carbon in the continuous carbon fiber reinforced silicon carbide is about 80% ~ 85%, the sputtering yield of protium, deuterium, tritium and helium atoms have the minimum values. The kind of incident particle has a significant effect on the sputtering yield. The sputtering yield of helium atoms is larger than that of tritium atoms and deuterium atoms. There is not much difference between the sputtering yield of deuterium atoms and tritium atoms, and both the sputtering yield of deuterium atoms and tritium atoms are larger than that of protium atoms. The sputtering yield initially increases rapidly with the increase of the incident energy and then decreases gradually. The incident energy of the protium, deuterium, tritium and helium atoms has the maximum value of the sputtering yield at 200, 400, 600 and 800 eV, respectively. When the incident energy of helium atoms is 100 eV, the sputtering yield decreases while the increase of the incident angle. These results can provide a certain reference for the application of continuous carbon fiber reinforced silicon carbide materials in nuclear engineering.