光子相关谱法测量BaTiO_3中极化团簇的弛豫时间

建立了测量晶体内部时间结构的双偏振滤波式光子相关谱实验装置.并用此装置对铁电单晶BaTiiO3中极化团簇的动力学行为实施了直接观测.结果表明,该方法可对BaTiO3中,空间周期为200 nm的极化团簇进行有效探测,其弛豫时间在微秒量级,并且随着温度的升高,弛豫时间逐渐减小,但在居里点处出现突变.     

碳团簇Cnn+(n=15)注入NaCl晶体的模型

６００ｋｅＶ的荷能碳和簇离子Ｃ＾＋ｎ（ｎ＝１－５）注入到ＮａＣｌ单晶,当入射粒子的速度ｖ大于玻尔速度ｖ０（＝３／１３７）时,能量转移主要是由入射粒子与靶原子的核外电子碰撞造成的。假定团簇中各原子的能量岐离大于它们的结合能时,团簇状态已经结束,各原子成为独立的粒子。     

碳团簇C_n~+(n=1─5)注入NaCl晶体的模型

600keV的荷能碳团族离子C+n（n=1─5）注入到NaCl单晶,当入射粒子的速度v大于玻尔速度v0（=c/137）时,能量转移主要是由入射粒子与靶原子的核外电子碰撞造成的。假定团簇中各原子的能量歧离大于它们的结合能时,团簇状态已经结束,各原子成为独立的粒子。利用Trim程序对碳团簇在NaCl单晶中的射程进行了模拟,得到团簇区域的长度为278－321nm,总射程为686nm。     

载能团簇直接诱发硅单晶转变成纳米晶结构

用扫描探针显微镜(SPM)观察了能量76keV、剂量1.7×10cm-2的N团簇离子注入Si(111)单晶表面的形貌。发现在此条件下,注入层已直接转化成具有一定粒度分布的纳米晶结构,并测量了形成晶粒的尺度及分布。用红外吸收实验检测了该实样的光学特性。实验表明,该试样对频带很宽的红外光产生了很强的均匀吸收,在红外光区,其透光度均保持在10%左右,表明其注入层已形成一种品质优良的吸光材料。     

MeV碳离子及碳团簇C2+注入PC膜的光吸收谱研究

研究了MeV碳离子及碳团簇C2 注入的聚碳酸酯(Polycarbonate,PC)膜.光吸收谱研究结果表明,离子注入在聚合物近表面产生了断键及缺陷,改变了PC的光吸收性质,在可见光区域有较明显的吸收,并且吸收边与注入离子的种类、能量和注量密切相关.X射线光电子谱(X-ray photoelectron spectroscopy,XPS)对PC的近表面结构和成分配比进行了分析,证实了以上的结论.     

团簇尺度诊断中瑞利散射信号波形获取与处理

在用瑞利散射法诊断团簇尺度的实验中,提出了相对强度测量法,为此设计了一个基于高速采样的信号波形获取与处理系统,提出了信号寻峰算法及拟合算法,完成了系统软件的设计,实现了对两路信号波形的获取与快速处理,并成功地应用于瑞利散射诊断团簇尺度的实验中.     

团簇尺度的瑞利散射测量中光电倍增管信号刻度与归一化处理

利用光电倍增管测量团簇的瑞利散射,信号幅度与团簇源背压有关,也与光源强度和光电倍增管工作电压有关.当团簇源背压变化范围较大时,散射信号幅度变化可能导致光电倍增管信号超出线性范围.为此,在不同的光源强度、不同的工作电压下对光电倍增管输出信号进行了刻度,得到了输出信号幅度随光源强度、工作电压之间的关系.用此关系.对不同条件下的实验数据进行归一化处理,得到了团簇散射因子随团簇源背压的关系曲线,与同类实验和理论结果相符.     

W及W-Mo团簇吸附H2分子的密度泛函研究

采用密度泛函广义梯度近似(GGA)的PW91方法,用全电子基组DNP对Wn(n=2-5)及W-Mo团簇几何结构进行优化,计算团簇电子结构参数,考察H2分子在W团簇上的吸附行为,并计算W4、W2Mo2团簇吸附H2分子的Mulliken电荷布居.结果表明:Wn(n=2-5)团簇为共价性成键特点,吸附H2分子的吸附能在0.0...     

核材料中子辐照损伤的团簇动力学模拟综述

核材料中子辐照损伤是影响核能装置安全性和稳定性的关键问题之一.由于难以开展大量的中子辐照实验来评估核材料的损伤机理,因此相关理论模拟至关重要.介观尺度团簇动力学(CD)模型由于不受时间和空间尺度的限制,是一种研究材料中子辐照损伤长时间演化的有效方法.本文综述了CD的模型、数值算法和最新进展,重点介绍了CD在典型核材料的...     

A calculation model for breakdown time delay and jitter of gas switches under hundred-nanosecond pulses and its application in a self-triggered pre-ionized switch

In this paper,a calculation model for the breakdown time delay and jitter of gas switches under hundred-nanosecond pulses is proposed and applied in a self-triggered pre-ionized switch.The effects of injection time of pre-ionization,pulse rise time,and the pre-ionization jitter are discussed and verified through experiments.It indicates that the pre-ionization should be injected when the electric field is high enough in the gap,injection after 80％peak-time can ensure its effectiveness.Then the statistical time delay jitter will be determined by the pre-ionization jitter,which is an intrinsic restriction of the self-triggered switch.However,when the changing rate of the pulsed electric field exceeds a certain value,the breakdown time delay jitter can be partly offset in the formative stage because the formative time delay has an exponential relationship with the electric field.Therefore,lower time jitter can be obtained under pulses with a shorter pulse rise time.In general,the results of the calculation model agree with the experimental results,and the experimental parameters which lead to a low jitter can also be used as a reference.     

Development of Operator Action Time for SBLOCA during Plant Shutdown Operation in Power-uprated Kori 3 and 4

The ECCS performance, which mitigates a postulated catastrophic failure of the main reactor coolant piping during the full power operation, is judged to cover the consequences of LOCA occurring in other plant operational states. During Mode 3 with an accumulator isolated and Mode 4, since the normal alignment of ECCS equipments is changed from that which is available during the power operation, a potential safety issue, which involved the performance of ECCS for LOCA during Mode 3 with the accumulator isolated and Mode 4, was identified in 1985. This study is performed as the plant specific shutdown LOCA program for the power uprated Kori-3 and 4, of which the nominal core power is planned to increase by 4.5%. We determine and verify the operator action time to initiate SI following a small break LOCA in order that the peak clad temperature of fuel does not exceed the 10CFR50.46 limit of 1,477.6 K.

We evaluate the 0.1524 m (6 inches) pipe break in the cold leg to develop the SI initiation time. There is a considerable margin to the 10CFR50.46 limit of 1,477.6 K in the case that the SI is manually initiated at 25 min after an operator identifies the symptom of a small break LOCA. However, in respect of the safe plant operation, we decide the operator SI initiation time as 15 min in order that the SI water is supplied to prevent the fuel heat-up during the blowdown phase of a small break LOCA. After then, we evaluate the applicability of the pre-determined SI initiation time to other small break LOCAs, which have a smaller break size, a lower initial decay heat level or a different break location. Since the peak clad temperatures of applicability evaluation cases are lower than those of the umbrella case, we confirm that the pre-determined SI initiation time can be applied to mitigate the small break LOCAs during the plant shutdown operation. The SI initiation time developed in this study will be used in the Abnormal Operating Procedure of the power uprated Kori-3 and 4 for the small break LOCAs during the plant shutdown operation.