A methodology to predict a fission gas release ratio of MOX fuel with heterogeneous microstructure

The objective of this study is to formulate a methodology to predict a fission gas release ratio of MIMAS MOX. An irradiated MIMAS MOX fuel with plutonium rich agglomerates was subjected to elemental analyses by electron probe micro analysis and secondary ion mass spectrometry in order to investigate xenon distribution. The results of the elemental analyses showed that the plutonium rich agglomerates at the periphery of the fuel pellet sample retained a high concentration of xenon as gas bubbles. Then, the results were used as reference data for modification of models in a fuel rod analysis code, FEMAXI-7. Using the modified FEMAXI-7, we applied an approach to prediction of fission gas release ratio of MOX fuel with plutonium rich agglomerates. In the approach, two separated analyses using FEMAXI-7 were performed for the plutonium rich agglomerates and the matrix. Fission gas release ratios obtained from the two analyses were processed through weighted-average with burnup ratios of the plutonium rich agglomerates and the matrix. Finally, the fission gas release ratios were compared with results of rod puncture tests. As a result of the comparison, it was confirmed that the proposed approach could well predict fission gas release ratio of MOX fuel with plutonium rich agglomerates.     

Simulation of ultrasound guided needle puncture using patient specific data with 3D textures and volume haptics

We present an integrated system for training ultrasound (US) guided needle puncture. Our aim is to provide a validated training tool for interventional radiology (IR) that uses actual patient data. IR procedures are highly reliant on the sense of touch and so haptic hardware is an important part of our solution. A hybrid surface/volume haptic rendering of an US transducer is proposed to constrain the device to remain outside the bony structures when scanning the patient's skin. A volume haptic model is proposed that implements an effective model of needle puncture. Force measurements have been made on real tissue and the resulting data is incorporated into the model. The other input data required is a computed tomography (CT) scan of the patient that is used to create the patient specific models. It is also the data source for a novel simulation of a virtual US scanner, which is used to guide the needle to the correct location. Copyright © 2007 John Wiley & Sons, Ltd.     

Modelling and analysis of a novel CT-guided puncture robot for lung brachytherapy

In this paper, we present a novel CT-guided needle puncture robot system with seven degree of freedoms. All basic requirements of interventional radiology can be met. To solve the space constraints and compatibility requirement, tendon-sheath transmission is used as the drive mode of the end-effector. According to the kinematics analysis of the robot configuration, the reachable workspace is obtained, which can completely cover the chest of patient. Based on the Jacobian matrix, dimension parameters are optimised for better flexibility and kinematic performance in the workspace. Since respiratory movement will cause real-time motion of the tumour, a method is proposed to decrease the puncture error caused by respiratory movement. And the feasibility of this method is verified by puncture experiment based on independent design of respiratory motion simulation device. It is proved that this method will lead to an increase in the puncture accuracy by 2.4 times. In addition, the CT compatibility of the robot is verified, and the positioning accuracy is also measured through the experiments.     

高压XLPE绝缘电力电缆的电老化与寿命估计

本文依据电老化定律,通过实验提出一种新的XLPE电缆的寿命指数n值的计算方法—直接累加法。大大降低了实际电老化试验费用。并且认为电老化主要是水树枝老化。求取n值的最好方法是逐级升压击穿法。     

穿刺手术柔性针路径规划技术现状和展望

微创穿刺手术由于具有创伤小、恢复快等优势,近年来在临床上得到广泛应用,主要用来进行组织活检、局部消融和局 部麻醉等操作。 目前穿刺手术使用的手术器械是斜尖柔性针,相比较于刚性针,前者可以避开重要的器官和组织,对患者的损 伤较小。 在手术过程中,有效的路径规划算法可以辅助医生提高手术的安全性和准确性,现有的术中路径规划算法的误差在毫 米量级,限制了其在临床手术中的应用,亟待探讨解决方法。 为此,梳理了穿刺手术中柔性针的路径规划研究进展,分析了影响 路径规划的因素,对穿刺针的路径规划算法进行了详细的介绍,指出了当前需要解决的关键问题,最后从最优路径选择、参数反 馈以及术中实时路径规划方法等不同方面出发探讨了柔性针手术穿刺针路径规划的未来发展方向。     

不均匀电场下CF_3I/N_2混合气体工频击穿特性试验

从工频击穿性能的角度探讨CF_3I/N_2混合气体替代SF6气体用于气体绝缘设备的可能性。通过工频击穿试验探究气压、混合比和电极间距三种因素对CF_3I/N_2混合气体工频击穿电压的影响,并与相同条件下的SF6/N2混合气体进行对比分析,提出使用协同效应指数C值判定混合气体协同效应类型及协同效应强弱的定量分析方法。结果表明,随着混合比、气压的升高,CF_3I/N_2混合气体工频击穿性能逐渐接近SF6气体,较高气压下的CF_3I/N_2混合气体更具有应用潜力。CF_3I/N_2混合气体工频击穿电压呈正协同效应,而且CF3I气体具有优良的自恢复绝缘性能。综合考虑工频击穿性能、液化温度和环境影响三种因素,在特定的场合下,CF3I含量为20%~50%的CF_3I/N_2混合气体有可能替代SF6气体用于气体绝缘设备。     

两台50MW汽轮发电机绝缘击穿故障分析与处理

本文介绍了宁夏石嘴山发电厂两台５０ＭＷ汽轮发电机出口母线发生短路故障后，定子线棒端部绝缘损伤情况，绝缘击穿原因分析及定子线棒绝缘的局部热压修复工艺，提出了消除发电机出口母线短路故障的措施和建议。     

侧脑室穿刺联合脑脊液置换治疗脑室出血的疗效观察

目的探讨侧脑室穿刺联合脑脊液置换治疗脑室出血的临床疗效。方法选取我院自1999年至2009年脑室出血(原发性或继发性)62例患者,随机分为对照组和实验组,实验组选取侧脑室前角行侧脑室穿刺,同时联合脑脊液置换,以清除脑室系统积血,比较实验前后的格拉斯哥昏迷评分(GCS)和神经功能缺损评分(NIHSS)。结果治疗第28dGCS、NIHSS评分,实验组均较对照组改善(P<0.05);结论侧脑室穿刺联合脑脊液置换治疗脑室出血是一种疗效确切,简单易行,安全可靠的治疗方法,值得在基层医院临床推广。     

Alternative mechanisms of increased eggshell hardness of avian brood parasites relative to host species

Obligate brood parasitic birds lay their eggs in nests of other species and parasite eggs typically have evolved greater structural strength relative to host eggs. Increased mechanical strength of the parasite eggshell is an adaptation that can interfere with puncture ejection behaviours of discriminating hosts. We investigated whether hardness of eggshells is related to differences between physical and chemical traits from three different races of the parasitic common cuckoo Cuculus canorus, and their respective hosts. Using tools developed for materials science, we discovered a novel correlate of increased strength of parasite eggs: the common cuckoo''s egg exhibits a greater microhardness, especially in the inner region of the shell matrix, relative to its host and sympatric non-host species. We then tested predictions of four potential mechanisms of shell strength: (i) increased relative thickness overall, (ii) greater proportion of the structurally harder shell layers, (iii) higher concentration of inorganic components in the shell matrix, and (iv) elevated deposition of a high density compound, MgCO₃, in the shell matrix. We confirmed support only for hypothesis (i). Eggshell characteristics did not differ between parasite eggs sampled from different host nests in distant geographical sites, suggesting an evolutionarily shared microstructural mechanism of stronger parasite eggshells across diverse host-races of brood parasitic cuckoos.     

抗电击穿装置的容量指标

根据影响介质击穿的主要因素,阐述了交流抗电击穿装置的容量指标问题。说明在确定抗电击穿装置的容量时, 不仅要考虑到被试样件两级之间的等效电容值, 同时还要估计到试样在击穿过程可能产生的最大击穿电流值