离子阱中热库诱导退相干的控制

对单个囚禁离子在热库作用下的退相干的控制问题进行了研究.本文提出的控制方法是基于消除自由哈密顿技术和脉冲重聚技术的结合.前者是利用一个经典大失谐激光场作用于囚禁离子来实现的,而后者是利用一系列的激光π脉冲来实现的.解析与数值表明,应用这种控制方法可以有效消除量子退相干且比纯粹应用脉冲重聚技术要好.     

<Emphasis Type="Italic">J/Ψ</Emphasis>production

For more than 25 yearsJΨ production has helped to sharpen our understanding of QCD. In proton induced reaction some observations are rather well understood while others are still unclear. The current status of the theory ofJΨ production will be sketched, paying special attention to the issues of formation time andJΨ re-interaction in a nuclear medium.     

铁基添加剂增强细水雾灭火性能的实验研究

采用实验模拟的方法,研究了添加氯化亚铁的细水雾在不同添加剂浓度、不同喷头压力下,熄灭不同性质的液体池火的性能。实验结果表明:添加有氯化亚铁的细水雾,其灭火性能发生了显著变化。存在一个最佳的灭火浓度,其对应的灭火时间最短,耗水量最少,灭火效率最高。细水雾喷头的工作压力和燃料的性质也对细水雾的灭火性能有影响:工作压力越大,细水雾的平均灭火时间越短。在相同的实验条件下,细水雾扑灭煤油池火的时间要短于扑灭酒精池火的时间。     

Relaxation-Induced Suppression of Vortex Disturbances in a Molecular Gas

The influence of thermal excitation on a finite-amplitude vortex disturbance in a shear flow of a molecular gas is studied in a model problem. The evolution of such vortex structures is typical of both the nonlinear stage of the laminar–turbulent transition and for developed turbulence. Since the excitation level was assumed to be comparatively low, full Navier–Stokes equations for a compressible heat-conducting gas were used in calculations; nonequilibrium was taken into account by the coefficient of bulk viscosity. As the bulk viscosity increases in the range of realistic values, the disturbance-energy damping rate in a weakly compressible flow increases approximately by 10%. The increase in the Mach number enhances the effect of disturbance suppression.     

矿渣粉加固粉土的理论分析及路用性能研究

提出了矿渣粉加固粉土的相关理论。将矿渣粉在加固土中的作用归结为火山灰胶凝效应和微集料填充效应,而火山灰胶凝效应又可进一步归结为水化作用、激发作用和离子交换作用;认为微集料填充效应与矿渣粉细度极为相关;用框图归纳了矿渣粉加固土的两种作用效应。进行了矿渣粉、石灰粉加固土无侧限饱水抗压强度、水稳定性、冻稳定性、温度收缩和干燥收缩等路用性能试验,并进行比较。结果表明,矿渣粉加固土所测路用性能指标优于石灰粉加固土。为工程应用提供了试验依据。     

Suppression of red cell diffusional water permeability by lipophilic solutes

The inhibitory effect of a series of neutral lipophilic solutes (methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-amylalcohol, n-hexanol, diethylether, nitrobenzene, and pyridine) on the diffusional water permeability (Pd, tot) of bovine erythrocyte membrane at 25 degrees C was studied in comparison to that of p-chloromercuri benzoate (pCMB). Permeability data were obtained by measuring the transmembrane diffusional water exchange time tau(exch) using an 1H-T2 NMR technique. Maximal inhibition by approximately 50% of Pd, tot was produced by 2 mM pCMB which completely blocked the membrane water channels in 20 min, hence suggesting the channel-to-lipid diffusional water permeability ratio of about 1:1. Furthermore, the maximal inhibitory effect of pCMB in combination with the lipophilic solutes was lower than that of pCMB alone. As pCMB does not interfere with the lipid bilayer, and provided that it blocks the water channels in solute presence as well, this confirms that the solutes induce an increase in the lipid-mediated background water permeability contribution (Pd, lipid) by the formation of aqueous leaks in the membrane hydrophobic barrier. However, faster but less efficient in permeability inhibition than pCMB (either alone or combined with solutes) were the lipophilic solutes alone. Taken together, the results indicate that the lipophilic solutes suppress the membrane total permeability Pd, tot by two opposing effects: a reduction of its channel-mediated part (Pd, channel) to the extent exceeding that of a simultaneous Pd, lipid increase. The inhibitory potency of the solutes tested appears to be correlated with their solubility in the membrane medium.     

Thermal decomposition kinetics of titanium hydride and Al alloy melt foaming process

Metal foams, now one of research foci, are a newclass of materials with low densities and novel physi-cal, mechanical, thermal, electrical and acoustic prop-erties[1—8]. Demands from high-tech make Al alloyfoam, which has much higher specific strength than ofpure Al foam, the new development focus[9—11]. Melt foaming process is one of the approaches tofabricate Al foam and Al alloy foam and their porestructure (pore diameter and porosity) has close rela-tionship with the thermal decompo…     

夸克随机组合机制与激发态重子的产生

从强子化过程的两个基本性质出发,在夸克随机组合框架上,得出了包括所有激发态在内的重子产生权重的一组基本关系．解释了“自旋抑制”和单态重子产额大的原因．最后,讨论了进一步确定激发态重子产生比例的条件和方法．     

Mode selective directional couplers for overmoded waveguide systems

Two types of directional couplers for transverse electric (TE) modes are described: short and multihole couplers, respectively. They selectively pick one mode out of a mode mixture in an overmoded circular waveguide system. Unwanted modes are either statistically kept at low level or are suppressed by destructive interference in the coupling waveguide. Mode selectivity and directivity in multihole couplers oscillate up and down with an increasing number of holes, finally reaching a minimum of approximately 20 dB, unless there are competing modes with rational fractions of the beat wavelength. A multihole coupler for the TE₀₂ mode (28 GHz, 63.4 mm waveguide diameter, 41 holes) and a length of 1.6 m shows a calculated directivity of 68 dB and suppresses the unwanted modes TE₀₁ with 34 dB (24 dB), TE₂₂ with 37 dB (45 dB), and further modes TE_m (<5, m<6) with 17 dB to 34 dB in forward direction (figures in parentheses are for unwanted modes propagating in backward direction).A short directional coupler for the TE₀₁ mode (28 GHz, 63.4 mm waveguide diameter) with 16 holes and a length of 230 mm shows a directivity of 55 to 100 dB between 27.9 and 28.1 GHz, suppressing the TE₀₂ mode with 35 to 80 dB, the TE₀₃ mode with 30 to 65 dB, and the TE₂₂ mode with 30 to 70 dB.     

Effects of ion-pairing reagents on the electrospray signal suppression of sulphonated dyes and intermediates

High-performance liquid chromatography/mass spectrometry (HPLC/MS) analysis of anionic species such as sulphonic acid dyes and intermediates requires volatile ion-pairing mobile phase additives. Six di- and trialkylammonium acetates were compared with tetraalkylammonium salts and ammonium acetate in the concentration range 0-20 mmol l(-1) as mobile phase additives for HPLC/MS of polysulphonated compounds. The effects of the structure and concentration of the ion-pairing reagents on the electrospray response of mono-, di- and tetrasulphonic aromatic acids and acid dyes were studied in detail. Further, five different mass analysers and instrument geometries were compared. A higher signal decrease is observed with linear geometry instruments in comparison to orthogonal or even Z-spray geometry mass spectrometers. The concentration of mobile phase additives has a significant influence on the abundance ratios of multiply charged ions in the mass spectra of polysulphonated compounds. The competing ions of sulphonic acids may also cause significant signal suppression.