Measurement and modeling of the effective thermal conductivity for porous methane hydrate samples

The effective thermal conductivities of gas-saturated porous methane hydrates were measured by a single-sided transient plane source (TPS) technique and simulated by a generalized fractal model of porous media that based on self-similarity.The density of porous hydrate,measured by the volume of the sample in the experimental system,was used to evaluate the porosity of methane hydrate samples.The fractal model was based on Sierpinski carpet,a thermal-electrical analogy technique and one-dimensional heat flow assumption.Both the experimental and computational results show the effective thermal conductivity of methane hydrate decreases with the porosity increase.The porosity of 0.3 can reduce the thermal conductivity of the methane hydrate by 25%.By analysis of the experimental data and the simulative result,the optimized thermal conductivity of the zero-porosity methane hydrate is about 0.7 W m-1K-1.     

基于环蕃类分子的铁氰化钾电化学存储和释放

通过利用合成的环蕃类化合物1与单壁碳纳米管(SWNTs)间的π-π共轭相互作用,将化合物1固定在SWNTs的表面,制备了1-SWNT修饰电极.利用化合物1氧化态和还原态与铁氰化钾分子之间不同强度的主客体相互作用,实现了铁氰化钾分子在1-SWNT修饰电极表面的电化学可控吸附和解吸.循环伏安和XPS实验结果表明,在本研究采用的实验条件下,铁氰化钾分子在电极表面20s内即可达到吸附平衡;当电极在0.70V下极化1000s后,大多数吸附的铁氰化钾可从电极表面解吸.基于此,制备了铁氰化钾的可控存储和释放的电化学器件,该器件不但可以重复进行铁氰化钾分子的存储和释放,而且多次重复操作表现出较好的稳定性和重现性.本研究在发展具有特殊用途的电化学纳米器件,例如分子搬运器、电化学开关等研究中具有重要意义.     

Isospin and symmetry energy study in nuclear EOS

This paper summarizes the isoscaling and isospin related studies in asymmetry nuclear reactions by different dynamic and sta tistical models. Isospin dependent quantum molecular dynamics model (IQMD) and lattice gas model (LGM) are used to study the isoscaling properties and isoscaling parameters dependence on incident energies, impact parameters, temperature and other parameters. In the LGM model, the signal of phase transition has been found in free neutron (proton) chemical potential dif ference Δμn or Δ...     

Tetrathiafulvalene (TTF)-based gelators:Stimuli responsive gels and conducting nanostructures

Tetrathiafulvalene (TTF) and its derivatives have been intensively investigated for conducting materials for more than 30 years.As π-electron donors,TTF and its derivatives can be reversibly transformed into the respective TTF.+ and TTF2+.Due to its reversible feature,the TTF unit has been widely employed as the building block for switchable systems.In recent years studies of conducting nanostructures of TTF derivatives have received more and more attention.One simple way to prepare nano-structures is throu...     

甲烷水合物导热机理的分子动力学模拟

甲烷水合物导热系数是甲烷水合物勘探、开采、储运以及其他应用过程中一个十分重要的物理参数.我们采用平衡分子动力学（EMD）方法Green-Kubo理论计算温度203.15～263.15K、压力范围3～100MPa、晶穴占有率为0～1的sI甲烷水合物的导热系数,采用的水分子模型包括TIP4P、TIP4P-Ew、TIP4P-FQ、TIP4P/2005、TIP4P/Ice.研究了主客体分子、外界温压条件等对甲烷水合物导热性能的影响.研究结果显示甲烷水合物的低导热性能由主体分子构建的sI笼型结构决定,而客体分子进入笼型结构后,使得笼型结构导热性能增强,同时进入笼型结构的客体分子越多,甲烷水合物导热性能越强.研究结果还显示在高温区域（T〉TDebye/3）内不同温度作用下,所有sI水合物具有相似的导热规律.压力对导热系数有一定影响,尤其是在较高压力条件下,压力越高,导热系数越大.而在不同温度和不同压力作用过程中,密度的改变对导热系数的增大或减小几乎没有影响.     

轻粒子产额及其关联的同位旋效应

用晶格气体模型系统地研究了热发射体的粒子发射特性,阐述了发射体系的同位旋对轻系统的中子、带电粒子和轻粒子产额,以及对轻粒子产额比和双产额同位素比的影响.发现轻粒子产额和产额比是复合系统同位旋的敏感观测量,而双产额同位素比几乎不依赖于体系的同位旋.     

微观半经典Vlasov框架下的巨偶极共振的系统学与同位旋效应

用微观半经典Vlasov方法研究了同位旋矢量巨偶极共振(GDR)的系统学.计算的GDR强度分布的峰位能量和宽度与实验结果是一致的,并与经验公式相符.计算还表明峰位能量有微小的同位旋效应,而峰的宽度几乎没有同位旋效应.     

含低剂量抑制剂体系气体水合物生成动力学

水合物管道堵塞是油气工业安全生产的重要问题之一, 目前低剂量抑制剂以其经济性、环境友好性等优点, 逐步取代传统抑制剂. 文中在8.5 MPa、4 ℃条件下, 1.072 L反应釜内, 采用甲烷、乙烷和丙烷混和气, 研究了含低剂量抑制剂聚乙烯吡咯烷酮(PVP)和GHI1的水合物生成体系反应过程, 计算分析了压缩因子和自由气量随反应时间的变化, 对比了在相同反应程度下添加PVP和GHI1后水合物含气量的区别, 探讨了GHI1组合抑制剂的抑制机理. 实验结果表明PVP和GHI1能抑制水合物生长, 不能有效抑制水合物成核; 添加PVP的体系, 在实验气体组成下, 甲烷乙烷进入水合物小晶穴, 并且甲烷优先进入小晶穴; GHI1对丙烷乙烷的抑制能力强于甲烷; 对比GHI1和PVP的反应过程, 认为协同剂二乙二醇丁醚的羟基和醚类结构加强反应体系中的氢键, 和PVP结合使用, 通过氢键和空阻达到抑制效果.     

中能重离子碎裂反应的同位旋效应及其消失

用修正的统计擦去模型计算了中能重离子碎裂反应产生的同位素分布的同位旋效应,发现随着(Z_proj–Z)/Z_proj的增大,碎裂反应的同位旋效应将逐渐减小直到消失.同时,研究表明碎裂反应的同位旋效应的消失主要是由擦去阶段的几何效应和随后的蒸发效应导致的.     

Measurements on diproton emission from the break-up channels of 23Al and 22Mg

Two-proton relative momentum distributions from the break-up channels ²³Al→p+p+²¹Na and ²²Mg→p+p+²⁰Ne at an energy of 60–70 A MeV have been measured together with two-proton opening angles at the projectile fragment separator beamline (RIPS) in the RIKEN Ring Cyclotron Facility. The results demonstrate the existence of diproton emission component from single-step ²He for highly excited ²³Al and ²²Mg.