Optimization of the three-dimensional electric f ield in IH-DTL

The tuning process of the three-dimensional electric field near the beam axis is very important in the optimization of the Interdigital H-mode Drift Tube Linac (IH-DTL). The tuning of the longitudinal field distribution, the Kilpatrik (Kp) factor, and the transverse dipole field have been discussed in detail, combined with the radio-frequency tuning process of the 53.667 MHz short IH-DTL cavity, which was designed to accelerate ²³⁸U³⁴⁺ from 0.143 MeV/u to 0.289 MeV/u in the SSC-Linac injector project at the Institute of Modern Physics. The flatness criterion and the tube tuning method are discussed in order to meet the beam dynamics requirements. In the tube tuning process, the energy gain error in the cells should be reduced to less than ±2%, and the Kp factor should be reduced to 1.6. The transverse dipole field and the method that uses a "plunger" to dismiss this dipole field are evaluated. The experience gained from the first cavity optimization benefits the tuning process of the three remaining IH-DTL cavities in the SSC-Linac project.     

Error and jitter effect studies on the SLED for the BEPC Ⅱ-linac

An RF pulse compressor is a device used to convert a long RF pulse to a short one with a much higher peak RF magnitude. SLED can be regarded as the earliest RF pulse compressor to be used in large-scale linear accelerators. It has been widely studied around the world and applied in the BEPC and BEPC linac for many years. During routine operation, error and jitter effects will deteriorate the performance of SLED, either on the output electromagnetic wave amplitude or phase. The error effects mainly include the frequency drift induced by cooling water temperature variation and the frequency/Q 0 /β unbalances between the two energy storage cavities caused by mechanical fabrication or microwave tuning. The jitter effects refer to the PSK switching phase and time jitters. In this paper, we re-derive the generalized formulae for the conventional SLED used in the BEPC linac, and the error and jitter effects on SLED performance are also investigated.     

Fast calibration methods using cosmic rays for a neutron detection array

An overall irradiation and calibration technique was introduced and applied to a test scintillation detector array. An integral conversion method was used to reduce the nonlinearity of the time difference spectrum, and to improve the position determination especially for positions close to the two ends of a long scintillation bar. An overall position resolution of about 3.0 cm (FWHM) was extracted from the residual analysis method and verified by a direct measurement. Energy calibration was also realized by selecting cosmic rays at different incident angles. The bulk light attenuation lengths for the four test bars were also determined. It is demonstrated that these methods are especially efficient for calibrating large and complex detector arrays.     

Modulation instability of an intense laser beam in an unmagnetized electron–positron–ion plasma

The modulation instability of an intense circularly polarized laser beam propagating in an unmagnetized, cold electron–positron–ion plasma is investigated. Adopting a generalized Karpman method, a three-dimensional nonlinear equation is shown to govern the laser field. Then the conditions for modulation instability and the temporal growth rate are obtained analytically. In order to compare with the usual electron–ion plasmas, the effect of positron concentration is considered. It is found that the increase in positron-to-electron density ratio shifts the instability region towards higher vertical wave numbers but does not cause displacement along the parallel wave number direction, and the growth rate increases as the positron-to-electron density ratio increases.     

亚硫酸氢钠溶液稳定性的探讨

从溶液的酸度、空气及光照、温度等因素对亚硫酸氢钠溶液的稳定性及滴定反应进行实验探讨,选择三乙醇胺(TEA)、甲醛、二乙胺四乙酸二钠(EDTA-2Na)、盐酸羟胺四种常用的螯合剂或强还原剂进行试验,结果表明EDTA-2Na作为溶液的稳定剂效果最好,其次是甲醛,最后是盐酸羟胺。TEA因为其强碱性会降低溶液的稳定性而不宜作为稳定剂。     

反应条件对Ni-CaO-ZrO2催化剂上CH4-CO2重整反应及积炭的影响

用共沉淀法制备了Ni-CaO-ZrO₂催化剂,并将其用于CH₄-CO₂重整反应。考察了反应温度、空速和反应物配比对催化剂性能和积炭的影响。通过热力学计算和实验表征研究发现,反应条件对CH₄-CO₂重整反应结果和积炭有重要的影响。由于高温条件同时有利于CH₄裂解和碳物种的及时消除,升高温度可以提高催化剂的活性和稳定性。增大空速则使CH₄的转化率和消碳反应的速率均降低,导致积炭量增加。同时,反应物配比对催化剂表面的积炭量也有很大影响;稍高的CO₂/CH₄摩尔比有利于抑制CH₄-CO₂重整反应过程中的积炭。     

免疫质谱法检测肝癌血清多肽标志物

建立免疫亲和富集分离与质谱分析相结合的免疫质谱法用于血清多肽标志物pep5的检测。多克隆抗体与蛋白A琼脂糖颗粒偶联用于捕获pep5,基质辅助激光解析电离飞行时间质谱检测标志物。本方法的线性范围为1～48 nmol/L,检出限0.2 nmol/L;回收率为93.0%～103.1%,相对标准偏差(RSD)为6.4%～11.8%;反复冻融3次pep5,检测结果稳定;检测临床肝癌/正常血清样本灵敏度为78.0%、特异度为90%。该方法方便、快速、准确,适用于临床样本中低浓度标志物的检测研究,对于癌症的早期诊断具有重要意义。     

分散固相萃取净化与液相色谱/串联质谱法测定牛奶中8类禁用药物残留

建立了牛奶中8类禁用药物的液相色谱-串联质谱( LC- MS/MS)检测方法.分析物包括5种硝基咪唑、7种β-受体激动剂、9种雄性激素、7种糖皮质激素、3种雌性激素、2种镇静剂、1种氯霉素以及6种二羟基苯甲酸内酯共40种禁用药物.样品以β葡萄糖苷醛酶/芳基硫酸酯酶在乙酸铵缓冲液中酶解,用氨化和酸化乙腈各提取一次.提取液经改良的分散固相萃取(QuEChERS)净化,浓缩后采用C18色谱柱分离(150 mm×2.1 mm i.d.,3.0 um).以甲醇和水(含0.1％甲酸)、乙腈和水分别作为正、负电喷雾离子化模式的色谱分离流动相进行梯度洗脱,多反应监测模式进行定性和定量分析.7种药物以内标法定量;33种药物以基质标准曲线外标法定量,氯霉素在0.02～0.4μg/kg; 39种药物在0.20～ 10.0 μg/kg范围内相关系数(r)均大于0.99;定量限(S/N=10)在0.07～0.93 μg/kg之间.分别以各个药物0.5,1和2倍MRPL( Minimum required performance limits)浓度水平加标验证实验,回收率范围60.3％～119.3％范围;相对标准偏差小于18.9％.     

高阶脉冲中立型偏泛函微分方程的强迫振动性

研究一类具高阶Laplace算子的高阶脉冲非线性中立型偏泛函微分方程的强迫振动性,利用Green公式和微分不等式方法将所讨论的脉冲中立型偏微分方程转化为脉冲中立型微分不等式的问题,获得了这类方程在三类不同边值条件下所有解强迫振动的若干充分条件.     

Marchuk模型周期解和概周期解的存在性与稳定性(英文)

本文讨论具有时滞和扩散的Marchuk模型.根据模型参数求出了模型方程的上、下解,利用单调方法和Liapunov函数分别证明了周期解和概周期解的存在性及其稳定性.