e+e-对撞中ψ(3770)非D(D)衰变的实验寻找

评述了以往与ψ(3770)非D(D)衰变相关的实验测量与研究,详细讨论了三种寻找非D(D)衰变的实验方法,即遍举、半单举和单举方法.这些方法对于在实验上寻找ψ(3770)非D(D)衰变具有启示和示范作用,有助于加深人们对粲夸克偶素态衰变动力学机制的理解.     

基于高精度理论截面计算的τ质量的再拟合

对于e⁺e^－→τ⁺τ^－过程在阈值附近的截面, 目前的理论计算精度已经达到10^－4. 基于理论截面的高精度计算, 利用极大似然函数方法, 重新拟合由e μ末态标记的τ⁺τ^－事例的扫描数据, 得到τ质量的测量结果为1776.98+0.44+0.12－0.51－0.13MeV, 其中第一项是统计误差, 由拟合程序给出; 第二项是系统误差, 主要包含能量刻度, 能散及本底估计等三方面的不确定性.     

Three-dimensional surface characteristics of a falling liquid film

Optical methods are described for examining the three-dimensional character of waves on a falling liquid film. This involved monitoring the motion of the local film surface normal through the use of laser beam refraction. The wavy motion was found to be primarily of a two-dimensional nature only for Re (equal to 4Q/v) less than 1500.

Surface characteristics were examined for Reynolds numbers from 217 to 4030 and for different distances along the direction of flow.     

Transducer resolution enhancement by combining different excitation pulses

This work presents a low-cost solution to improve the axial resolution of an arbitrarily loaded and backed piezoelectric transducer. The proposed solution is based on the use of different excitation pulses and, in particular, the combination of two excitation pulses. The characteristic parameters of the second pulse, i.e. amplitude and time delay with respect to the main pulse, are obtained by studying the waveform of a reference pulse emitted or received by the transducer. This reference pulse is the transducer's response to a generic excitation pulse which has the same shape and duration as the main pulse. The work also presents a procedure to estimate the characteristic parameters of the second excitation pulse by means of the electrical simulator SPICE. Then, to illustrate the effectiveness of the simulation, the simulated and experimental values are compared through two experimental cases.     

氯气的制备及性质一体化实验改进设计*

目前在化学教材中涉及氯气制备、性质的实验存在一些不足,如反应物用量大、反应时间长、反应分开进行及对环境污染大等。因此,在传统实验与现有改进实验的基础上,将氯气制备、漂白性、酸性、氧化性等多性质检验与尾气处理综合进行一体化改进设计,不仅操作简单、有效减少试剂用量,且对环境污染小,体现绿色化学思想。     

基于“教学评一体化”的化学探究活动一般思路方法建构*——以“物质的分离与提纯”复习课为例

针对学生面对化学实验探究问题无从下手的情况,以物质的分离与提纯这一类探究实验为例,通过“教学评一体化”的教学模式引导学生建立解决“物质分离与提纯”探究实验的一般思路方法。     

Existence and Uniqueness of Solutions to Singular Higher Order Two-point BVPs on Time Scales

This paper investigates the existence and uniqueness of solutions for singular higher order boundary value problems on time scales by using mixed monotone method.The theorems obtained are very general.For the different time scale,the problem may be the corresponding continuous or discrete boundary value problem.     

“双抛物型”参数方程的探讨

本文提出"双抛物型"参数方程的概念,并对其图形、性质等进行了讨论.     

Forced convection — axial conduction between parallel walls with unequal heat fluxes

Laminar flow heat transfer is computed for a situation in which a fluid moves along a parallel plate channel with unequal wall heat fluxes (one wall is insulated). The fluid enters the heating section through an upstream region which is perfectly insulated. This situation serves to describe an upper bound for the commonly encountered case of double pipe heat exchangers with identical thermal conditions. A control volume approach has been employed for the numerical work enabling a fast calculation for the thermally developing regime in the parallel plate channel. The merits of the adopted procedure are assessed by comparison with other results available in the literature for the one-region and for the two-region problem.     

甲基噻吩在HY分子筛上的吸附、脱附及转化行为

由NH₄Y分子筛制备了HY分子筛,运用N₂吸附、NH₃-TPD和Py-FTIR等手段表征HY分子筛的物化性能;采用智能重量分析仪(IGA)方法研究了甲基噻吩(2-甲基噻吩、3-甲基噻吩)在HY分子筛上的吸附-脱附行为;采用程序升温脱附-质谱(TPD-MS)联用手段研究了甲基噻吩在HY分子筛上的转化行为。结果表明,在200 ℃下 2-甲基噻吩和3-甲基噻吩在HY分子筛中的强B酸上发生强化学吸附作用,与B酸结合后生成了甲基噻吩的碳正离子结构进而发生了歧化反应、脱烷基反应以及裂化反应;与2-甲基噻吩不同的是,3-甲基噻吩与HY通过一定的氢转移反应生成了3-甲基四氢噻吩,且200 ℃吸附条件下3-甲基噻吩比2-甲基噻吩更容易发生裂化反应。